"According to genetic theory, there is very close to an even chance that both children in a two family will be of the same sex.

I need help with this question.."According to genetic theory, there is very close to an even chance that both children in a two family will be of the same sex. The possibilities are 15 couples have two children each. In 10 or more of these families , it will turn out that both children are of the same sex; 30 couples have two children of each. In 20 or more of these families will turn out that both children are of the same sex, which of the possibilities is more likely and why?"