As their children grew, their younger child always wanted to be Batgirl, Spider-Girl, or Wonder Woman when playing, and was a girl wearing a dress in every picture drawn with fat crayons. Picture: Washington Post

Looking back on it, there were signs from a very young age.

Vanessa and JR Ford have two children, both born male. By 18 months, their youngest child was having major tantrums when getting dressed.

This child was only happy in hand-me-down clothing that looked more girl-centric, rather than boy-centric.

As their children grew, their younger child always wanted to be Batgirl, Spider-Girl, or Wonder Woman when playing, and was a girl wearing a dress in every picture drawn with fat crayons. Their second-born was insistent about this and never wavered. Finally, their child told them in no uncertain terms: "I am a girl."

Today, Ellie is a happy and very loved six-year-old (almost!) girl whose closet is full of dresses, who plays with her older brother, Ronnie, as she always did, who is called sister and daughter, who has a great group of friends and goes to a public school where she is welcomed and that she loves.

Her parents say she is happier, lighter and more herself now that her family is letting her live as she feels, in her words, in both her heart and her head.

The family is one of the subjects in a new documentary, Gender Revolution: A Journey With Katie Couric, which premieres on the National Geographic channel. We spoke with Vanessa and JR so they could explain what this process has been like for them, as parents and as a family.

Q: When did you realise that perhaps something was going on?

Vanessa: Both of our children, around three, liked to play dresses. Ronnie used to play dress-up, loved ballet and loved pink. But by four, that was gone for him. Which makes sense in the development with kids. Ellie did the same, but around four[wanting to wear dresses] got much stronger. Other things we noticed with Ellie that we didn't with Ronnie is when she had these dresses on, or anything she perceived as girlie, she would act differently. When she wasn't in these clothes, she wouldn't engage with people, she was much more difficult for us. When she did have these clothes on, she was smiley, playful. In retrospect, we look back to when she was pre-verbal. For a while between the ages of 18 months and three, we would have a lot of trouble getting her dressed. Eventually we thought maybe she had a sensory issue. So we started to try to get super-soft hand-me-downs. More gender neutral clothes came to us, things that would be considered a little more non-masculine. Once she could tell us she didn't stop.

Q: Was there a "lightbulb" moment when you realised, oh, this is really something?

Vanessa: It was the Frozen and Lightning McQueen birthday party. We had a "son" in a tiara. At the end of that party, when everyone left, I said, "You are my favourite princess boy!" And she stopped and said: "Mom I'm not a boy. I'm a girl in my heart and my brain." I said, "It's time for bed, go brush your teeth and get in bed!" and I jumped on the internet. Up popped different articles that described just what she was saying. We reached out to groups and people and over the next three months it really became clear.

JR: That was the moment. Before that, we kind of just went with the flow of letting Ronnie and Ellie just kind of be themselves. We didn't know what was going on, and she couldn't describe to us how she was feeling inside. It took about a year-and-a-half to get to that lightbulb moment, after we had started noticing something was unique about her.

Q: What was the next step? Were you resistant?

JR: Vanessa found Children's National Medical Center has a gender and sexuality clinic. She scheduled an intake to really find out what's going on, were we doing the right thing. The summer [after Ellie's 4th birthday] was kind of that whole research phase where Vanessa took a lot of time to research and find support groups. That led into the fall, when we finally got to the intake. That summer there was a lot of educating us and our family about what was going on.

Vanessa: She had told us in every way possible. I was so naive and said things like: But you know girls are born with these parts and boys with these parts. And she said, "But mom that can't be true because I'm a girl." This was not about her body, this was about her brain and her heart. By end of preschool, she had already asked Ronnie to call her sister and he was doing that.

Q: Were you hesitant at all about moving toward her living as a girl?

Vanessa: We were both reticent and also moving forward. I don't know, do we call her a girl? We finally got her pink swim trunks and a rashguard that said "girls rule." We were visiting family and she tantrumed when we put a life vest on her and it covered the words. She said "No one will know I'm a girl."

Q: How did you let people know?

Vanessa: We wrote a friends and family letter. Went to every parent in her class. We continue to have an evolution of that letter at her new school. We also talked to the school she'd be entering so she could move in as a girl. The District has very strong rules about gender, so they changed her gender and her name. At this point, it's been almost two years since she told us, and she's just who she is.

Q: What has it been like to parent your children through this?

Vanessa: The biggest thing we have done as parents is just be whirlwinds around her. There's a safety in this city. We want to advocate so people with young kids going through this same thing can find resources and know they are not alone. It's been really helpful. Our day-to-day lives very much do revolve around this, because we have a safe, happy kid in a safe, happy school, and that's not the case for so many.

How has this changed your lives?

Vanessa: It's changed my life in a specific way. I was a teacher for 14 years. During the last school year, I needed more time to be mom both emotionally and literally. I loved my students and my school, but I needed to find a job that allowed me to use my skills but have more flexibility for appointments and advocacy. I'm now the director of education for a nonprofit. It's been a really nice balance. At the [National Geographic screening], I had my old principal and my new boss sitting next to each other. They both knew what I was coming into the organization with, and what I needed from my career. I've been making choices around my career that allowed me to be an advocate and stay connected.

JR: As a dad, those stereotypical traditions have been broken. I internaliae a lot. Now I've been able to go and see a therapist and unpack emotions; there are a lot of complex issues to deal with. But it takes a lot for me to open up, and just going through this journey with Ellie has definitely humbled me and has broken the ceiling I thought I had for loving and supporting both our kids.