How IS your family? or How ARE your family?

The correct way to word this question is “How is your family?”

The reason is that while family refers to a group of people, it refers to the group of people as a single unit, or collection. Nouns like this are called collective nouns, and in American English, collective nouns take singular verbs. (In British English, many collective nouns can also take plural verbs.) 

Here are some other collective nouns, shown in example sentences, all with singular verbs:

• The visitor group was asked to wait outside the museum until 10 am. (group is a collective noun, was asked is a singular verb)

• I think our team is going to win a lot of games this season. (team is a collective noun, is going to win is a singular verb)

• This year the 5^th grade class has four students from Asia. (class is a collective noun; has is a singular verb) 

However, the collective noun police is an exception. It takes a plural verb, as in this example: