1. How many are there in your family?

2. How many people are there in your family?
3. How many members are there in your family?

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Are they all aceptable?
Which one is the most common?

1 answer

They are all acceptable. No. 1 is most common.

The word "there" could be omitted in each, but it is probably best to leave it. When responding to the question, "There are.." would be the appropriate beginning.