Kristin Collier had been married to her husband, Fred, for 12 years when he told her he wanted to be a woman.

13 years on and Fred has become a woman called Seda, but the couple are still married and living together with their two children and Kristin’s romantic partner, Richard.

It’s an unusual set-up, but for this transfamily, it works.

Kristin and Fred met when they were 18 and 30 respectively, they quickly fell in love and were married a year later.

The marriage was a happy one, and those 12 years were the best ones of Kristin’s life, “but now it’s really great too,” she told The Independent.

Not everything was right under the surface though.

“Everything was so easy with him but when I’d go away he’d get really depressed,” Kristin explains. “He’d often drink which he didn’t normally do, and he would write me letters about what a horrible person he was. He hated himself so much.”

It was when Kristin had been staying at her mother’s for a week that Fred called and said he needed to talk to her about something.

Although she’d never previously suspected her husband might want to be a woman, there was something about that phone call that brought back memories of two incidents from ten years earlier when she’d found two of her dresses ripped at the waist after Fred had tried them on.

“I’d put those incidents to the back of my mind, though. To me he was perfect,” she says.

Kristin and Fred before he became Seda

But when Kristin got home, Fred told her he’d bought some women’s clothes while she’d been away and had never felt more like himself, or rather herself. He was elated, but also scared.

Fred had grown up in a tiny town in Wyoming and knew nothing about transgenderism - “He thought it was a sick weirdness inside of him,” Kristin explains.

Kristin’s initial reaction was a mix of confusion and terror: “I was sure my whole life would fall apart,” she says.

She began questioning her marriage, asking herself if the love could be real when the man wasn’t. “Was our relationship real? Was all of my joy in the last 12 years real or was it a lie?”

Her roles as a wife and mother were about to be turned upside down.

Kristin, a communications specialist who’s now 44, never thought about leaving her husband though. “I just loved this guy, he was too awesome,” she says. “The person I needed to help me get me through my grief was my best friend, and that was Fred.”

It was a lot to take in, but the couple didn’t make any drastic decisions. They decided to take things step-by-step and just do whatever seemed right to them: “We didn’t actively decide to stay together, it just never made sense to split,” Kristin says.

“Fred was the most amazing person I’d ever known, so I didn’t want to leave.”

Over the next three years, Fred went to therapy to make sure he was 100 per cent set on becoming a woman.

It was only once Fred had decided he absolutely couldn’t go on living as a man that the couple told their two young children, then aged five and three.

Kristin and Fred with their two boys

Fred became Seda, Daddy became Maddy, and he became she overnight.

Physically transitioning took a lot longer, but Seda started by wearing women’s clothes at home, which was tricky for Kristin at first: “I wanted to understand and see but also didn’t because I knew it would be the end of the husband and wife picture that we had,” she says.

But Seda and Kristin’s relationship gradually became more like that of two sisters - Kristin took Seda to get her ears pierced, they went shopping together, and she even helped pick out synthetic breasts for Seda.

The couple stayed married for financial reasons and also because neither of them wanted to be apart from their kids, but Kristin was in a tricky situation - she was single, yet legally married, which she says was “awkward and confusing”.

Meeting men who didn’t already know about Seda was difficult as it was an unusual situation to explain.

It wasn’t until she met a man called Jack* and became totally transfixed by him that she realised she was completely heterosexual.

Fortunately for Kristin, who has written a book about her story, Housewife: Home-remaking in a Transgender Marriage, Jack was very open to her unusual family set-up: “I explained the whole situation to him and luckily he was totally OK with it,” she says.

Kristin, Seda and their two sons

Her relationship with Jack ended, as did one with a music teacher called Ben*, and for the last two years Kristin’s current partner Richard has been a part of the family.

“I feel more like a widow than a divorcee,” Kristin says. “The person I was in love with is dead and gone. The chemistry is gone.

“We still get along very well but there’s no attraction there for either of us which makes it possible for someone else to come in without jealousy and awkwardness.”

Seda now lives in a private wing of the house shared by Kristin and Richard in Eugene, Oregon, plus Kristin and Seda’s two children.

They eat all their meals together and live harmoniously - Richard does all the cooking, Seda the laundry, they both get on very well and the kids love having three adults to play with.

When they meet new people, Kristin now introduces Seda as her “parenting partner,” which a lot of people love the idea of.

With her now very feminine looks though, Seda doesn’t attract as much attention as she used to.

The fact that Seda didn’t grow up with the cultural backlash that shapes women, yet experienced so much of it later on, forced Kristin to look at her own womanhood and what it means to be a woman.

She’s now firmly of the belief that gender identity is created by each individual: “At first I thought I knew all about what it meant to be a woman, and now I know I don’t.

“I can’t now define what being a woman is because now I think it’s up to you, it comes from inside of you.”

Through her experience, Kristin wishes other people would see their challenges as opportunities and embrace them: “We all have major transitions in our relationships - whether someone has an affair or our child has a disability - and the way we approach those challenges as a couple is how we will grow our compassion skills.

“Those skills will stay with us for the rest of their lives and will allow us to have deeper relationships with everyone.”