Defining a family has legal significance, of course, for matters such as taxes or employee benefits, but this question is even more complex when trying to understand how people think about what constitutes a family, more generally. Understanding which types of arrangements “count” as a family and which do not reveals a lot about shifting cultural expectations and social norms.

New research by Brian Powell, reported by ABC News, suggests that having children is a key ingredient for many people in defining a family, particularly when asked about unmarried or same-sex couples.

“Children provide this, quote, ‘guarantee’ that move you to family status,” Powell said. “Having children signals something. It signals that there really is a commitment and a sense of responsibility in a family.”

For instance, 39.6 percent in 2010 said that an unmarried man and woman living together were a family — but give that couple some kids and 83 percent say that’s a family.

Thirty-three percent said a gay male couple was a family. Sixty-four percent said they became a family when they added children.

However, despite what labels others may place on you, most respondents thought self-identification was more important:

Sixty percent of Americans in 2010 said that if you considered yourself to be a family, then you were one.