1) The majorities of our family members is in London.
2) The majority of our family members is in London.
3) The majority of our family members are in London.
4) The majority of our family member are in London.
5) None of these
Rule ⇒ After such expressions as one – half of, two – thirds of, a part of, a majority of, (a) use a singular verb if a singular noun follows the of. (b) use a plural verb when a plural noun follows the of. ‘Family members’ is the noun and it is plural so, plural verb ‘are’ will be used.