It's tough to call, but there are plenty of kids who find their gender identity at an early age, me included. A lot of people assume that gender identity is learned through parenting and gender roles in society, but it's not entirely true. There was a man named David Reimer, who was born male with his identical brother, but lost his penis in a circumcision gone wrong. His parents decided to change his sex into a girl to avoid the burden of being a male without a penis. He never acted/felt like a girl, and when he parents confessed, he immediately went to being the guy he was, but it was a lot of damage, and he committed suicide.
I do think it's a little odd that his father is transgender as well. I hope no one is pressuring his decisions for him, or it could have traumatic effects. I'm constantly on the fence about transgender children taking hormones. I know it's better at an earlier age, but there is no guarantee that what they want is a sure thing.