New to BYC, but I've been lurking for quite sometime and have learned a great deal. Right now I have 10 chickens and three guinea chicks. My older batch of four chickens are approximately 11 weeks old. I bought them straight run at TSC to begin my flock. The rooster of the group, Roberto, isn't a Plymouth Rock like the others. TSC told me he must've gotten mixed in during shipping, and that they're not sure what breed he is (this was when he was only four weeks old). He has always been the sweetest bird, but lately has been getting agressive with the hens and with me. Today he pecked me and screeched when I tried to pick him up. I'm guessing it's his age and developmental changes? They free range almost all day so I don't think it is boredom. I also have six red ranger pullets that are five weeks old that I keep separate from the older ones because he has gone after them as well. 1. Any ideas on Roberto's breed? 2. Should I get rid of him because of his increasing aggressiveness? We have three small kids that I worry about. Thanks!