Cathy, 49, who works in sales, lives in Hertfordshire, England, with her husband Andy, 50, a classic car restorer.
The couple have two children: Elliot, 14, and Ana, who now identifies as Alfie, and is in the process of transitioning from female to male.
The family are part of a British television documentary on the process of gender transition, as three female-to-male individuals tell their stories. The film is hard-hitting and candid, and includes footage of an operation to construct a new penis.
Alfie's story is just as jaw-dropping in its way, not least as this eloquent, forceful young man makes a strong and sympathetic spokesperson for the transgender community.
The Equality and Human Rights Commission cautiously estimated that one per cent of the population was transgender, after a survey in 2012.
High-profile transgender celebrities, including Caitlin Jenner in the United States and the former boxing promoter Kellie Maloney in the UK, are helping to raise awareness.
But Alfie's story shines a light on children suffering gender dysphoria, or gender identity disorder, the description of someone unhappy with their biological sex who wishes to belong to the other one.
His father shows me a picture of a cute 14-month-old rolling down a haystack on a farm visit. "I knew when I was growing up," Alfie says, "that I didn't want to do the things girls did. People thought being a tomboy was a phase, but I knew I wouldn't change. I didn't want to wear girl clothes. I hated the way they fitted to me."
When Alfie was eight, he told Cathy he was a boy in a girl's body, but she put it down to tomboyishness. Cathy says: "It was all there in front of us. People would ask me what children I had, and I would say, 'I've got a girl and a boy, but my daughter is such a tomboy, it's like having two boys.'"
Alfie admits to feeling a sort of constant frustration: "I was told I would change and get interested in make-up, but I could never see it happening. And I couldn't express how strongly I knew this."
Physically, Alfie was developing in a feminine way, nonetheless. "At some point, my friends and mum and dad were noticing I needed something under my T-shirt, but I refused to wear a bra. I used to wrap my chest in bandages to try and flatten my chest."
He lifts up his T-shirt to show me the binder he now wears; it's a compression garment which is designed to flatten everything out comfortably and safely.
"The first time I put it on, it felt amazing."
Puberty and the start of periods came at 14, thanks to incipient polycystic ovaries. Alfie is grateful that they are sporadic, but admits he was devastated when they began.
By then, Alfie says, there were dates with boys in an attempt to be "normal", but he was attracted to girls and concluded to his father that he was a lesbian. Even so, "the title lesbian didn't fit me. I felt like I was mixing and matching things together."
The girls he then asked out (when still known as Ana) knew he was having gender issues and were supportive. At the beginning of Year 10, Alfie discussed the possibility of being transgender with a close friend. But it was only after an appointment with a paediatrician in 2013 that Alfie spoke to his parents.
"I was having my hormone levels tested, as my periods were so irregular. The paediatrician then brought up the topic of gender transition. So on the way home, I said to mum, 'I think I'm transgender.'
"And I said, OK," his mother adds. "By now, I wasn't surprised at all."
His father's reaction was equally supportive. "I just said, 'Right, what do we do now?'" But inevitably there were concerns: "I thought Alfie would get bullied," Cathy says. "And I thought how frightened he would have been when he realised, and that I hadn't been there to comfort him."
Alfie admits that the seven months between realising he was transgender and telling his parents were difficult, but gave him time to get used to the idea. It was still daunting coming out to the world: "I knew my friends would be cool, and they were, but it was scary, the day I finally said it."
His GP, and teachers at Sir John Lawes School, Harpenden, were wholeheartedly supportive. Since then, Alfie has dressed and identified as a boy, and begun the slow process of counselling prescribed before any physical transformation can happen.
The NHS does not offer testosterone before the age of 18, although Alfie was eligible to receive it privately once two years had passed since he officially "came out".
Six months ago, he began receiving testosterone injections, one every three weeks, which he will need for life. "My voice started dropping first," he says. "You could hear it crack."
Cathy adds: "He was so excited to be growing hair. He dragged me upstairs to the mirror to see."
The next stage will be soon: "top-half surgery", which means removal of breast tissue. At some point he will have a hysterectomy, but "lower surgery", the creation of a penis, is not on his to-do list: "I'm not desperate to have it. I don't think it would make me feel any more masculine. I've lived 18 years without it."
He says candidly: "Of course, I am sexually frustrated, but for me, having sex will never be like for a cisgender person." (Cisgender describes someone who identifies with the gender they were born with.) "I'm not too bothered. Who knows what will happen in the future?"
Alfie has had to deal with abuse and prejudice. He shrugs off most of it with wit and insouciance. But he is clearly frustrated a recent year-long relationship broke up largely because the girl's father did not like him.
There is comfort in being part of the growing openly transgender community, and his involvement in the Channel 4 programme is due to his drive to help other youngsters.
His parents are rightly proud of their son. "He's never felt sorry for himself, always looked ahead," Cathy says.
Andy would counsel other parents who may wonder if this is their child's story, too: "If there is a situation you are unsure of - get research. Never reject them. It's not a life choice."
He adds: "For me, the worst thing was the change of name. For months, I couldn't do it. Then I saw a programme on bereavement and I knew I needed closure on my relationship with my daughter. I had to let that child go. So we went away to Barcelona for a long weekend, and I made a farewell card, and addressed it to Ana. And after Alfie read it, we burnt it on the beach together. And then it was fine."
