Hello. Yes, most of the time plural and masculine words refer to generality (mostly with family) Mis primos, mis tíos, mis hermanos --> it means all of them, women and men or just men. BUT it´s more common to say 'mis hermanos varones or mis hermanos hombres' when you´re trying to be very specific. :)

I can say, in addition, that when in a place there are only female members you can say, "mis hermanas", "mis cuñadas", "mis tías", "mis primas", etc.

Hello Katie, yes, you're right!, in most cases you use masculine plural to reference mixed gender family members, for example "los abuelos"; the word "los" is plural and masculine but it's referencing both genders, if you want to make reference to just your female grandmothers you should use "las abuelas". PD: I apologize for my broken English, i hope i answered your question.

All precedent answers are right. Just one point to clarify: when you say "the sons" you are talking about your male children. When you say "los hijos" without more details, you are talking about all your male and female children.