I had children in my teens and became a grandmother two decades ago. I’ve always thought how lucky I was to get pregnant so easily, and how heartbreaking it is for people who can’t. I liked the idea of being a surrogate, but my husband wasn’t keen. By 2012, we had divorced, and I’d taken care of my parents and older brother, who sadly passed away. I’d turned 50 and thought, if I’m going to do this, it needs to be now.

The organisation Surrogacy UK said they had never had a surrogate of my age, and that I needed to find a clinic that would work with me as a gestational surrogate. I had gone through the menopause, so the embryo would be implanted in my womb (as opposed to artificially inseminating my own eggs). I emailed 42 clinics and almost all said I was over their age limit. But one clinic, 15 miles from my home in Birmingham, said yes.

I went with my daughter to a social event to meet other future surrogates and people searching for one. I got chatting to a man called Gary, who introduced his partner, Andy, and as we all sat together, something clicked: we had the same sense of humour. We grew closer, and by Christmas I knew they were the couple I wanted to help. When Gary got the official call on 31 December 2012, he phoned me in floods of tears. He was overjoyed.

Over the next three months we drew up an agreement about decisions throughout the pregnancy, birth and afterwards. The boys both wanted me involved in their family’s life, so their child would know how they came into the world, and I felt the same.

They needed to find an egg donor, but the waiting list at my clinic was 12 months. I was staggered when a friend from work phoned me out of the blue and said, “I’ll be your egg donor.” She was 29, had two children and just wanted to help. She went through two rounds of egg collection, which gave us three good-quality embryos, and three days later one of them was transferred to my womb.

Unfortunately, it failed, and the boys were devastated. We had a break for a few months, before implanting both remaining embryos to give us a better chance of success. Six days later, I had heartburn, just as I’d had more than three decades earlier, and I knew. Under the pretence of giving Gary an early birthday present, I invited the boys over and gave him a box wrapped up with a ribbon. He opened it, took out the positive pregnancy test and cried his eyes out.

At the six-week scan, all three of us heard the words, “We’ve got a really strong heartbeat there. And another really strong heartbeat there.” It was a good job I was lying down, because it was a bit of a shock, but a wonderful one: I was carrying twins.

I understood immediately that the twins would never be mine, that I was just looking after them, as if they were my nieces or nephews. I used to stroke my stomach, not bonding with them because they were my children, but because they were the children of my best friends.

At the 12-week scan, when my name was called and the three of us stood up, we were told, “Oh no, this is just for the parents.” I said, “OK, that’s fine, I’ll wait here. You go in, boys.” Eventually we all went in, but after that we switched hospitals, and I was booked in for a caesarean section. I went into spontaneous labour one month earlier, on 19 March 2014, 33 weeks and five days into my pregnancy. My daughter and Gary were in the room with me when Marnie was born at 1.40pm, weighing 3lb 12oz (1.7kg), and Dexter at 1.41pm, weighing 4lb 4oz (1.9kg). They were taken to the special care baby unit and stayed in hospital for three weeks. I stayed for six days, then came home and expressed milk for them.

When the babies were ready to be held, Gary and Andy insisted the nurse hand each twin to me first, so I would be the one to give them to their parents. The best part of the whole experience for me was seeing their faces, knowing these babies were theirs – something they never thought would happen.

Now the twins are nearly four and we see each other every week. I love watching them play with my grandchildren. When Marnie says, “We came out of your tummy, didn’t we, Auntie Sue?” I feel an overwhelming sense of love and pride.

• As told to Moya Sarner

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