I too am keeing two males together...one was very young, and has grown up in the cage with an older male. They are both sexually mature now. I put a female in there the other day, while cleaning a cage, and heard some noise. I looked over to see the younger male was trying to breed with the female. The larger male moved around, then the younger male grabbed him by the neck, trying to breed with him too. When I removed the female, they were fine again. I should also add, that I have sold one of those two adult males, and now can keep my males singly again, which I prefer.
Hatchlings can be kept together for upwards of one year. After they start coloring up nicely, I would keep a close eye on behaviours.
John Eddington