Transgender and under 12 years old?

I fully support the transgender community! But I am curious to what others feel towards transgenders that are extremely young. I myself am not transgender so I have never felt that I do not belong in my body. It must be an awful feeling . But for those that are 6 or 9? I cannot say I understand completely(why I am asking this question so I can get some feedback). It's probably my ignorance so I apologize in advance. But how do they know of such things at a young age? My little brother and my little cousins have no clue  about making themselves something completely different. I feel like media plays a big part of that. Are parents exposing their children to such things? Are they jumping to conclusions that because their son plays with dolls they can't be gay? Because they're daughter likes G.I Joe they can't be lesbian? What about toys having no gender? What makes parents believe that their kid NEEDS to go through with this process? Was wondering if anyone with experience could share. Or anyone just sharing their opinion.