When Jesse Toksvig-Stewart was born 27 years ago, her parents crossed the words mummy and daddy out of their baby record book and wrote Mum and Mumma instead. “The book is full of black lines because so much of it wasn’t relevant to our family,” says Jesse.

This was in 1988 and two-mother families, two-father families, and even divorced families and reconstructed families were all far less common.

Spool forward to three years ago, and the arrival of a new baby in Jesse’s family. The child, a girl, was adopted by Jesse’s mother, Peta Stewart, who split up from her other mother, the broadcaster Sandi Toksvig, 17 years ago. Peta is raising the little girl (whom we won’t name for reasons connected to her adoption) alone and when Jesse went to buy a baby record book, she was shocked to discover that every single one stocked by the bookshops was geared to the outmoded stereotype of one mother, one father and lots of assumptions about early shared moments.

It seemed a travesty to Jesse, whose experience of family life has been so different. She was raised, with her sister Megan and brother Theo, now 25 and 21 respectively, in the heart of conservative Surrey: in Guildford, the kind of town for which the word leafy was coined. It wasn’t an alternative place, like Brighton or Hebden Bridge, yet Sandi and Peta and their brood were almost universally accepted, and Jesse can count on the fingers of one hand the number of times they were made to feel uncomfortable.

“Most of our friends were conventional families with heterosexual parents and we didn’t know any other families like us,” she remembers. “My parents were trailblazers – these days there are plenty of lesbian couples with kids, but not in the late 1980s.”

When she was born, her mothers were so worried that someone from social services might come and take them away that they hid themselves away for weeks.

Sandi and Peta, says their daughter, had fallen in love at first sight; Sandi is “a hopeless romantic” and, at the beginning, the couple hunkered down and luxuriated in their new-found relationship. When, a few years later, they decided they would like children, they turned to their closest friends, a heterosexual couple, for help.

The male half of that partnership, Chris Lloyd-Pack, agreed to donate sperm and Jesse and her siblings were the result. Meanwhile Chris added to his own family, upping from two to four kids with his then partner and later having another two children with a new partner. It all made for a family that sounds a lot more complicated than it felt, according to Jesse. She had three full-siblings and six half-siblings, including a brother who was only two months younger than she was.

“When we were all out together he and I used to pretend to be twins,” says Jesse. “It made things simpler.”

Jesse and her two mothers, Peta Stewart and Sandi Toksvig.

Home life was similar to any other family, with one or two significant differences. “There were fallouts and arguments, happy times and sad times,” says Jesse.

“But what was really good was that there was no differentiation in our parents’ roles. They were both working parents – Sandi was doing programmes like Call My Bluff on BBC2 and the News Quiz on Radio 4, and Peta was running a hotel – we grew up without expectations about who did what. So when I was at university and a shelf broke, I was the one who fixed it, not any of my three male housemates.”

Chris Lloyd-Pack was more like an uncle than a father – “He’s a massive hippy, and it was completely understood on all sides from the start that he would have no parenting role” – and the Toksvig-Stewart children have always called him Chris.

Jesse doesn’t remember a moment when Sandi and Peta sat them all down to announce that they were going their separate ways and that in itself, she believes, says something about how well the whole split was handled. Do two-mother couples do it better? “I think perhaps they do,” says Jesse. “You hear of bitter divorces where everyone is incredibly unhappy and the children say their whole lives have been affected, and there was never anything like that in our family.

“Maybe women are more forgiving; maybe they are more able to put the children first. I’m not saying it wasn’t hard for us because it was, especially in the first few years, but our mums kept things as normal as possible and they really did stay good friends. We all still went on holiday together and we’d always be all together for our birthdays – there was none of this celebrating it with first one parent and then the other.”

When Peta had breast cancer 10 years ago, Sandi – now married to Debbie Toksvig, whose daughter is Jesse’s stepsister – was a great support through all the surgery and chemotherapy.

Jesse and her siblings stayed in Guildford with Peta, but spent every other weekend with Sandi: even now, says Jesse, she rarely goes more than a fortnight without seeing Sandi. At the moment she is away filming for her first series as presenter of the BBC television quiz show QI, but they talk on the phone all the time.

Jesse with her sister and their mothers, Peta, left and Sandi.

Though physically like Peta, her biological mother, Jesse is often told how much she resembles Sandi, to whom she isn’t genetically related. And now Peta, who is a foster carer, has adopted her little girl, Jesse says she has a new insight into how her family worked. “I’ve been very involved with my new sister’s life and it has made me realise that it’s not about genetics at all – it’s about being in someone’s life and it’s about loving them.

“You’re there to give them meals and put them to bed and you’re there to pick them up when they fall over, and you’re there to read to them and talk to them. You’d die for them and you’d kill for them – and that’s what makes you a family, not whether you’re biologically related.

“It’s made me realise that this is how Sandi feels about me. It might sound corny, but love really is the most important thing. If you’ve got that, everything else is almost always going to be OK.”

Today Jesse and her boyfriend Adam live in a flat in the house where she grew up, and where Peta still lives – so she sees plenty of her new sister. Moving in with a man, she says, was truly alternative in her family. “There are so many gay women on both sides of our family that being heterosexual is definitely different.”

Jesse is a photographer – when she graduated from York St John University in 2011, Peta and Sandi attended the ceremony together – and she specialises in weddings. It’s a job that’s shown her how similar every couple is. “People think gay couples will want something different, that it will somehow be different because they are two men or two women getting married,” she says.

“But the thing is, they’re all exactly the same. Gay couples, lesbian couples, heterosexual couples: wedding days are all about exactly the same things: romance, hope, families and fun. There’s no difference at all, and that says a great deal.”

So, too, does Jesse’s decision to publish the baby record book she made for her new little sister, which she wrote with a friend, Kat Willott, who, she says, had a conventional family of mum, dad, and three sisters.

“At first it was just going to be for our family, but then I realised there are so many families out there whose lives don’t fit neatly into the boxes the baby record books have decided they should,” she says.

A page from My Amazing Family, the book Jesse published with her friend Kat Willott shows the first page dedicated to the baby’s milestone moments.

The book, My Amazing Family and Me, is designed to include every sort of family, and makes no presumptions about who the parents are, how long the child has been with them or how much they know about his or her background.

“We were very careful not to eliminate anyone. We really do believe this is a baby record book that any family, whatever they look like and however the babies have arrived, can use,” says Jesse.

So instead of asking about the baby’s birth, the book asks about his or her arrival: “It could be the day the baby arrived at the house, if it was an adoption,” says Jesse. And when it comes to milestones, it’s up to parents to record the important events they want to, rather than steering them towards particular times that might have happened before the family was together.

Most important of all, of course, there is no assumption that there is a mother and father. The fresh pages are poised for an outpouring of love for a new child, but how that outpouring is catalogued is very much up to each individual family, which, in Jesse’s experience, is exactly as it should be.

My Amazing Family and Me by Jesse Toksvig-Stewart and Kat Willott is available from uglyduckbooks.co.uk, £15.99