Born a girl named Elysia, known as Ellie, Ellis Saggers, 17, never felt comfortable as a female.
By the age of seven, he had cut his hair short and shunned female clothes in favour of baggy jeans and boys' underwear.
But it was not until years later when his mother Tracy Saggers, 43, encouraged him to watch a television documentary about transgender teenagers he finally realised he was actually male.
Then, in November 2015 Ellis announced his new identity to the world – via Facebook.
He said: "It said I had come out as transgender to my family and no longer wanted people to refer to me as she and I was changing my name."
"Everyone was so supportive and said how brave I was, it was really amazing," he said.
Mrs Saggers, of Littleport, Cambridgeshire, told of how, as a little girl, Ellis loved dresses and dolls.
But as he grew older, he became more of a tomboy – a stark contrast to his sister Maia, 16, who loved anything girly.
By aged seven, he would only wear clothes from the boys' section of high street stores.
Then female, strangers would sometimes even mistake him for a boy when he went out with his family.
"Ellis – then Ellie - wore her hair cropped short and dressed in baggy boys' clothes," said his mum. "And instead of Barbie dolls for her birthday, we bought her Action Men and Lego."
"I didn't mind. Ellie had always had a mind of her own and I was happy for her to explore who she was," she said.
Sadly, though, not everyone was as open minded.
At school, Ellis found himself the victim of cruel bullies.
On one occasion, a classmate yanked down his trousers to prove he was a girl.
As he grew up, he began to experience changes in her body – which he hated.
"Ellie hid her breasts and hips under oversized clothes and her shoulders broadened," said Mrs Saggers.
"She walked with a masculine swagger – so different to Maia's feminine gracefulness.
"As her body became more womanly, the Ellie I loved – bright and sparkling – began to fade.
"I knew she was dealing with something difficult, but she refused to open up."
At 14, Ellis came out to his parents as gay.
But still, he did not feel happy in his own skin.
Sinking further and further into depression, he would avoid looking at himself in the mirror and "virtually ignore" his period when it came, pretending it was not happening.
"My little girl seemed so confused and full of self-hatred," said Mrs Saggers. "There were days when she couldn't get out of bed and refused to see her friends.
"Life for her was confined to the house, where she'd mope around, or curl up in bed with the curtains drawn.
"I had always loved her, because she knew her own mind and was different to other girls.
"But now it seemed her difference was making her miserable."
Then, in November 2015 Mrs Saggers caught a Channel 4 documentary called 'Born In The Wrong Body'.
The show charted the lives of a handful of transgender teenagers as they navigated transitioning into the bodies they had been born to live in.
Hearing the girls featured talk about how much they hated their breasts and periods made her realise that Ellis could be transgender.
She said the idea had crossed her mind before, but that seeing the documentary had been like the final piece of a puzzle slotting into place.
"Watching these teenagers battle with their identity, as they discovered they were transgender, hit close to home," said Mrs Saggers. "These kids were on the telly – but I had one in the room upstairs."
She continued: "If Ellie knew and came to terms with who she truly was, perhaps she could finally be happy."
The next morning, Mrs Saggers gently broached the idea of the documentary to Ellis, suggesting he watch it.
It was a week before he worked up the courage, but when he did, he said it resonated with him immediately.
Straight away, he told his mum that she was right – he was transgender, and wanted to be a boy.
Together, the pair attended a doctor's appointment and is currently waiting to see a specialist at the Tavistock centre.
He penned a Facebook essay, which attracted hundreds of likes and comments.
Since transitioning into Ellis, a shop worker, has never been happier and has put his body confidence issues behind him.
He said: "It was amazing when mum told me about the programme. It helped me out a lot as she made me feel like I wasn't on my own.
"Knowing I had a supporter and her being there for me was really helpful."