Of course Jazz never went through puberty and so never developed sexually (or a sexuality), but we all had crushes and experienced puppy love as children. Gays report being attracted, even at that stage, to the same sex, while straights were attracted to the opposite sex. I had my first "boyfriend" at 2, promised to marry another boy at 6, and was "in love" with another boy at 9. Jazz had a serious (childish) crush on Victoria and not Amir.
There's no reason to believe he would've been gay.
He's not even "fem" anymore.