Of cause the household roles are based on gender. If you walked into the house after school, went to hug your mum and realized it was a bearded man with Hilary Clinton hair wearing an apron you would freak out. Now I can not speak on behalf of society but at least where I live the following rules apply:
The role of mother is fulfilled by a female
The role of father is fulfilled by a male
The role of sister is fulfilled by a female
The role of brother is fulfilled by a male
The role of uncle is fulfilled by a male (however this depends on how disfunctional a family is)
It is important to note that a genders family role is dynamic and ever changing.