I have birds just like this, they are Cochins and appear to be roosters. The blue one has a very red comb and my hens have barely any visible comb at all at that age. The black one appears to be developing red wattles which is always a telltale sign for me that they are roosters. The good thing is though, Cochin roosters tend to be very docile and if they grew up together, they typically dont fight very much. It would still be advisable to keep them for a while to know for sure and keep your favorite if they turn out to be roosters for sure. The black one will develop very very shiny and pointy feathers on its back and saddle if it is a male. If it is a female, its feathers will get very round and fluffy. Im almost 100% sure the blue one is a boy,but he is very pretty.