One hamster per cage regardless of species.It is extremely risky to house any sort of group,and it isn't even natural for same sex pairs or groups to live permanently in the wild together
Separate them as soon as possible even if they're not obviously fighting.Keeping several hamsters together does constantly give stress to both hamsters,and even if they're not outright attacking each other the stress and risk of fighting when you're not around isn't worth it.I know they're adorable,and it may seem cute when they're young and not giving off hormones to make fights more likely,but that is never a reason to take such serious risks with animals I'm sure you love and would never want to get hurt or worse