They can start crowing at all ages. I had one roo that waited until he was 4 months. The roo I have now is crowing at 8 weeks and I have heard people swear theirs started crowing at 3 weeks! hahahha!Most likely all boys, we did the same thing, we bought three frizzles and sizzle from our feed store and one started crowing first then they all started making noise then they all started crowing. What breed are they?