The answer is 3 million
It's near 3.3 million to be exact according to the United States 2010 Census report on Households.
This is up from just 700,000 when was the last census was conducted in 2000.
It also shows how economic conditions, growing populations and changing trends now means that more siblings are living together.
The overall census provides a great snapshot of the United States which now has a total population of 308.7 million.
Hispanics outnumber African Americans as the largest minority group in the country and there are more than 650,000 same-sex households.
