When it comes to getting pregnant with twins the mother is the one that usually carries the genes for twins.
If someone in your family had or has twins then your chances of having twins go up.
For example if your sister had twins then it could be highly likely that you would have twins as well but not always.
Or if your mother had twins then you may have the genes to have twins yourself.
Having the genes to have twins runs in families just like having the genes to have triplets etc.
Not everyone will get pregnant with twins, triplets etc and not everyone will even have more than one gender such as boys and girls.
My coworker only has all girls while another coworker has all boys.
So you may only give birth to only one gender of baby or you may give birth to multiple genders of babies.