"I found her with a knife and pants down": Emma was born a boy but knew she was a girl at four years old.

Megan Hayes says the moment she realised her young daughter was different from her two older sons is still clear in her mind.

“I found her in the room just with a knife and pants down, and she tried to cut off her own penis,” Hayes told Karl Stefanovic during a 60 Minutes interview aired on Sunday.

The four-year-old, Hayes said, “wanted to cut it off. She just didn’t want it there. She didn’t think it belonged there.”

Born Ronan, Megan and husband David Hayes say their third child began showing dysphoric behaviour early on in life, preferring dolls, wigs and dress-ups to more traditional boys toys.

"We just put it down to a phase, and thinking 'okay well, she's just a bit different to my first two boys' and left it at that," the Caboolture mum said before admitting that the cutting incident was the turning point for the family, realising that this was far more than just a phase.

"She only ended up with a little scratch, thank God," Hayes said of the memory.

Emma was finally diagnosed with gender dysphoria at the age of eight, which is when the Hayes' removed Ronan from primary school and reenrolled their child as Emma.

Now aged 12, Emma has begun high school and is undertaking hormone blocking treatment to ensure her transition continues throughout puberty.

When asked if they believed they had made the right decision for their child, the Hayes replied, "I think we did."

David continued, "I couldn't see a future for Emma if we had of forced her to be Ronan, I don't think she would be here."