Joseph is five months old. He has dimpled arms, a bright smile and a shock of black hair that stands out against the snowy white bedspread he is lying on. He might be Hollywood's take on childhood – and Hollywood is pretty much where he came from. Joseph's father, Kit Ram, is a single man and Joseph was conceived with the help of a surrogacy agency based in Beverly Hills. Joseph snuggles into the crook of Kit's arm while Harry, the Guardian's photographer, perches above the bed on a chair. I sit in the window bay, my legs and head tucked out of shot. We are all the same age, Harry, Kit and me, just three men in their late 40s, going googly for a baby. In the next-door driveway, a mother chases after a child riding a tricycle. In the garden opposite, a climbing frame sits beside a weeping willow. There are children everywhere. Even Harry has a two-year-old toddler, and has proudly shown off the photographs. I am the odd one out, the sole childless man.

It gets worse. Joseph pushes his face into his dad's T-shirt, leaving Harry struggling to get his shot. He asks for help: can I get Joseph to look in my direction? I have no idea what interests a five-month-old baby, so I wave my arms and squawk like a wounded pterodactyl. Kit and Harry stare aghast. It would have been less embarrassing had my head revolved 360 degrees.

Shortly afterwards, I leave the room and go down to the garden. A familiar feeling of distress has sneaked up on me. It is not just the happy daddy scene in the bedroom, but the whole leafy suburban environment. Kit's semi-detached house stands on the kind of street I grew up on. A week earlier, I had interviewed Brian Tessier, another single man my age who had chosen to go it alone by adopting two boys, Ben and Bryce. We talked about our childhoods in the 60s and 70s. Brian told me, "Growing up was very much, Wait Till Your Father Gets Home. That's exactly what my family was like." Mine, too. My father read Treasure Island aloud and built a tank-like sledge out of welded steel that was a joyful menace in the snow. But he had the job and my mother stayed home. Fathers were never expected to do very much. They just had to be.

Back then, childless men aroused suspicion. There is a 1955 poem by Allen Ginsberg, A Supermarket In California, that runs: "I saw you, Walt Whitman, childless, lonely old grubber, poking among the meats in the refrigerator and eyeing the grocery boys." I hope things have changed, but I am a child of a different age and perhaps I carry the old prejudices with me. The truth is, I feel out of place among family men.

Brian and Kit wanted children so much that they both ended long-term relationships with partners who didn't want a family. Brian is round, bearded and so relaxed he verges on the floppy. The home he shares with his boys could be the American version of Kit's, set in leafy Boston rather than Bedford. "I drive a people carrier. I live in the suburbs. That's me. I love it, but I'm thinking about writing a book called My So-Called Alternative Life, because it's all so normal." Brian was on the cusp of 40 when he decided to go it alone. That was eight years ago. He was a lawyer in a private practice, specialising in family law. He now works as a corporate lawyer ("The health benefits are good"). He has some help with his sons. "I've had male and female au pairs. The male applicants get picked last, but obviously I don't care. We're close to a Swedish boy who taught them to play football." Brian is gay and split from his partner when marriage became legal in Massachusetts: the change in status revealed their different priorities. His partner wanted to carry on partying, while Brian valued domesticity. "The hardest part of coming out in the 80s was knowing you would never have children." He expects to remain single a while longer. "Try telling a gay man you're the father of two boys. You will not believe how fast that man can run." Yet, he admits, "Part of me is glad, there is no threat from another parent."

A few months after the end of his relationship, Brian was out on a call as a family lawyer. An adoption had failed and a 10-month-old child was about to be taken into care. In the melee, the social workers asked Brian to hold the baby. "That was the moment that set off the biological clock," he says. "I even asked the social workers if I could take the child. I knew them. They knew me. They told me, 'You know that's not how it works, Brian.'" There is an obligatory 10-week course to become a licensed foster carer in the US, and Brian knew he would have to complete it before he would be considered for adoption. "I was on a road trip, staying at a B&B in Charleston run by a Unitarian minister. He and I talked in the mornings over the  muffins and he asked me what I wanted. When I told him I wanted to be a father, he asked what was stopping me. I went right out into the parking lot and made a call."

Brian knew the system and expected that he would have to take an older, disadvantaged child. He didn't expect it to happen within weeks of finishing the course. He was at the airport waiting to board a plane for France when the call came. "I've still never been to France," Brian says. Ben was two years old but his developmental age was closer to nine months. "He didn't talk. He had his own language of grunts and other noises. He understood a few words of Spanish, but no English." Brian wondered what he was getting into. "I had a stuffed animal with me, and I sat in a corner and waited for him. He came over a few times, just touching me and running away. Then he came over, stroked my face and said, 'Daddy'. The social workers were in tears and I wanted to bawl, but I just about held it together."

A single man who wants to start a family on his own has two options, either adoption or surrogacy. The first British man to go it alone was Ian Mucklejohn, whose triplets – Lars, Piers and Ian – were born through surrogacy at a San Diego clinic in 2000. It is difficult to get figures on the number of men who have followed Ian and Kit's path. Natalie Gamble, a family lawyer based in London, blames government policy, which currently holds that surrogacy is such a serious undertaking it should be restricted to couples. "Men go abroad, and then they try to stay under the radar," she says. "There is no legal framework to support these fathers." At the Centre for Family Research at Cambridge University, Lucy Blake is in the process of setting up a study but admits "we know very little about these families". Gamble's law firm has helped 16 men over the past three years, six of them straight and 10 gay. "Information is anecdotal, but our perception is that it's definitely a growing trend," she says. Melissa Brisman, a US lawyer with her own surrogacy agency, Reproductive Possibilities, tells me she has helped 50 men in the US and UK over the past few years. Like Gamble, just over a third of her clients are straight men.

If celebrities are any pointer to long-term trends, we could be seeing more single fathers by choice. Footballer Cristiano Ronaldo has a son, also called Cristiano, who was born in a San Diego clinic in June 2010. The singer Ricky Martin has twins, Matteo and Valentino, born in a Los Angeles clinic in 2008.

California clinics boast a success rate of 85%, as long as the egg donor is under 30 and the man's sperm is healthy. But this is not the key reason single fathers choose California. Under state law, the clinics must use two different women, an egg donor and a "gestational carrier", the woman who undergoes pregnancy. This division of labour effectively opens a grey area that allows the biological father to be named the sole legal guardian. The reason that agencies such as Reproductive Possibilities exist is to match egg donors and parents with the gestational carrier demanded by California law, as well as to keep all the contracts straight. British law does not yet accept this ruse. Natalie Gamble explains that the woman who gives birth is the legal parent in Britain, regardless of a Californian contract or DNA tests: "The situation gets even more complicated if the surrogate is married," she says. "Then her partner would have a strong claim to be the co-parent." In effect, the law encourages fathers to keep a low profile, which is why Gamble launched a campaign group, Brilliant Beginnings, to lobby for the rights of solo parents using surrogacy.

Kit remembers vividly the anxious experience of taking his baby son home from the US. "I made sure I was one of the first there, to beat the queue. I went up to the man with Joseph in my arms and showed him Joseph's American passport. He asked, 'Where's the mother?' I said, he was born through surrogacy and I have all the documents in this bag, so you can either hold the baby or hold the bag. He said, 'I'll hold the baby, please.'" Kit now faces the problem of getting Joseph registered as a UK citizen, a process that can take years, as Ian discovered.

Brian Tessier runs a helpline for prospective single fathers, 4114Dads. He warns that surrogacy has very high and often hidden costs. "The agencies quote $60,000-100,000, but it is often closer to $300,000." Kit kept a spreadsheet of his costs: "I recorded air fares, food, where we stayed and there was not much change out of 150 grand." I assume we are talking dollars. "No. Pounds."

The woman who gave birth to Joseph lives in rural Washington, and Kit paid for her flights from Seattle, her hotel bills while she rested after IVF, and all her hospital fees. Kit describes her as a farm girl. "She's quite a simple woman, but lovely." Egg donors, on the other hand, are supposed to be anonymous, although Kit knows more than he should. "She's a fairly well-known model and photographer, so, with the internet and everything, she couldn't remain so anonymous. She must also be quite business-minded, because she has sold a lot of eggs. Some fathers pay about a quarter of what I did. I decided to go for the best I could afford."

Kit sold his business to pay the fees. "I had a property management company, which I sold for half a million pounds." Like Brian, he also ended a long-term relationship with a partner who didn't want children, though in his case the ex still helps out. "He works with children, and he's been supportive. He just didn't want any of his own." Since becoming a dad, Kit has also fallen out with his older brother and sister. They had hoped he would help out his nephews and nieces after selling his business, Kit says. "My brother remarked that Joseph might be cute, but was a waste of money."

I don't have children because I am infertile, though these days that is only half a reason. There are so many options, so many ways around the problem. Like most childless couples, my wife and I have considered them all. Even with IVF, the possibility of conceiving a child diminishes rapidly in your 40s – not to mention the fact that standing in a hospital cupboard and masturbating into a plastic container eventually palls. We knew instinctively that egg donors and surrogacy were not for us. My brother has an adopted son, my much-loved nephew, so adoption was an attractive option. Brian is evangelical about it: "Men don't know they can do it. They are amazed when they're told they can adopt. I want to send a message to the average guy that they can be fathers. There are kids who need parents." It is possible for men in the UK to adopt – though a social worker tells me, on condition of anonymity, that the best route would be to become a foster carer first, and then to adopt. When we talked about adoption, my brother joked, "Of course, it takes a very special kind of person." We laughed, but ultimately we decided that he was right. We sensed that we might not be special enough.

It took me a long while to face up to never having children. Yet however much I regret it, I wonder if part of my problem is feeling that childlessness has left me on the outside of things. Brian tells me he was once playing with his boys on the beach when a man stopped to talk. "He asked if they were my sons, and when I said yes, he told me that he had wanted children, but that dream had died for him." I can relate to the story, but wonder if it is a story about a man who wants children? Or a story about someone who knows he is a little cut adrift from life?

My wife and I came to our decision together, of course. If you are a single parent, that responsibility is yours alone. If you are a single father and you opt for surrogacy, the freedom can seem limitless. Even the most infertile man can have his sperm sieved and graded until one is found that can withstand being injected into an egg. If necessary, the sperm can be surgically removed from the testes. Ian learned this on his return to California, six years after the birth of his boys, when he met a fellow father whose sons had been born from the same donor's eggs. He was shocked to find that his counterpart was over 80 years old. Ian's sons were born when he was 54, which most people would feel is old. It is old, but it is a lot younger than 80. "By looking at a distance at a situation like mine, I had seen the selfishness that is a huge part of surrogacy," he now says. "What I saw was not a pretty sight."

Brisman confirms that her clients tend to be quite mature. Gay men start surrogacy in their late 30s and older; straight men such as Ian tend to be 45 to 55. "What I find with single men, is one of two things," Brisman says. "Either they have been very successful in their careers and built businesses and they've not had time to meet anyone. Or they've had a very bad divorce and are afraid to get married and have their businesses threatened, or their custody threatened, and they would just prefer to go it alone. They know with surrogacy they won't have these issues." Brisman is convinced that the tendency of family courts to award custody to the mother is a key driver in the rise of heterosexual single fathers. For one father, however, the issue was more simple. US lawyer Steve Harris last year told Men's Health Magazine, "I wanted a family and now I have one. I don't have the need for a relationship. My son cost me $200,000. A wife would have cost me much more."

Here in the UK, Gamble is less sure that family law is an issue. "I don't think our thinking is as evolved on that issue. It's more a case of dads – like single mums – just deciding to crack on with it on their own." Brian Tessier, however, firmly agrees with Brisman. He is currently advising a New York stockbroker who called his helpline. "He's looked into custody arrangements and said, 'Why would I want any part of that?' Another guy I'm advising is in the process of adopting. He has a girlfriend with two children from a previous relationship, so the intention is to create a mixed family together. But he is adopting alone and he has no interest in giving up his parenting rights."

Listening to these stories of powerful financiers and businessmen starting families alone, one could be forgiven for imagining baby farms, run by batteries of nannies. Brisman sets me straight. "What you find is, the guys are so grateful, they are more involved than is traditional. They change diapers and do all the other things you just would never expect. They do it all." I believe her. Brian, Kit and Ian have all gone to these lengths, almost to extremes, not because they were more vainglorious or more ashamed of being childless. What they do have is an out-of-the-ordinary capacity to care for others.

Kit describes himself as the baby of his family. His mother was 46 when he was born. His brother was already 11 and his sisters were 16 and 17. His father died when he was only 10. After leaving school, Kit became a television dancer. "I danced on Top Of The Pops and The Word. When my mother had a fall, I returned to Bedford and stayed as she became more disabled. At first, I thought it was temporary and I would continue my career." He needed money, so took a job at a property management company. "After 11 weeks, I decided I could do the job better than them. I started out with £2.50. If I really knew what I was doing, it would never have happened. Sometimes it's better to plunge in."

In the last years of his mother's life, Kit would get up several times in the night to help her to her commode or bring her water. "Then I would bathe her and dress her before going into work." His mother was a matriarch, he says. "She was the glue that held the family together. When she died, I found my place in the family had gone, too. Instead of being at the centre of things, I became an afterthought." He describes himself as spoiled. He believes it was the sense that he had lost his place in his family that led him to want children of his own. Yet, as far as I can see, his willingness to be a carer is really the heart of his story.

Ian is also the child of elderly parents. His father suffered from dementia that required round-the-clock attention. Ian's life was circumscribed by his father's mood swings, violence and incapacity. Like Kit, he started a business that gave him the freedom to work around his parents' needs: a summer school, which celebrates its 40th birthday this year. Like Kit, he is the type of man who plunges in, and his story has the same distinctive blend of gentleness and steel. A sense of duty combined with a defiant do-it-yourself streak.

As Brian and I discuss our fathers, he brings it up to date. "My sister had her children first, and I saw my father playing with them. I mean, now he even cooks for his grandchildren. I don't remember him ever doing that." I often hear this from men my age, the discovery that fathers who were once cold and distant have evolved into warm and engaged grandparents. There are few things any of us can do to contribute simply to a better world. Caring for children is perhaps the only guaranteed route. I regret that I will never be a father myself, yet I take comfort knowing that what I am missing is this: being a real father, not simply an empty figurehead, a guy who has managed to squeeze out a kid or two. There are many other ways I can be a carer.