I like games with hair color variety, independently if in the family or outside. Personally I don’t care if they physically don’t look alike, provided that they act as family members.
Anyway, you can think there is a Saiki in the world making unnatural hair colors common and natural.
I don`t really pay much attention if the hair colors are consistent in the family, wathever color they have you can just say they dyed it. On the other side i really prefer if there is some variety in the hairstyles, be it color or the cut.
I'm more concerned about the different skin colors of the models (and I'm not talking about different races). Like for example Big Brother - everyone has their own skin color