How old are they? The one with the black neck is definitely a cockerel. But if the other is ~5 months, then it's a pullet. I don't know what type of chicken. I think they are mixes. You can add more chickens, but you have to do it carefully. The new ones have to be of a similar size and it helps a lot if you have a look but don't touch policy for a while. So say you get younger chicks, put the cages next to each other so they can see and interact, but not get hurt. Then when they are bigger, you can combine with little problems.I really would love it if I could keep them and add 2 or 3 more. Can anyone tell me what type of chickens they are?View attachment 1224665