Yes, it is a cockerel. Also I don't think they are red stars. The two gold ones look like they maybe Buff Orpingtons but I'm not sure what the one with black around its neck is (probably just a mixed breed).
The bird in question is a cockerel and your birds are not Red Stars (Red Sex Links) as they lack the yellow legs, the typical white tail feathers, and the white underfluff of Red Sex Links. Also RSL (Red Star) cockerels are primarily white with some red flecking for patching in the saddle area. Your birds appear to be mixed breeds.