when does family become family?

i was walking home drunk one night. this night if i am being precise, but that little bit of information will only really be of assistance if on the off chance you are reading this within the next 4 - 5 hours or so... which i doubt. comment if you are though =D

as i was saying, i got thinking. when do people become a family??

i have a group of friends.. not biggest by a long shot. but this group of friends is special because they are my group of friends.
4 of them are in long term relationships.. (two sets of two)... the rest are irrelevant for the purpose of this blog.

one of them. lets call him hayson! has been with his partner for nearly 2 years. hayson's longest relationship. they now live with each other.
the other, lets call his madam, has been with his partner for over 2 years, nearly 3.

this lead me to think. at what point do their respective partners become family..
Hayson lives with his partner. does this make them family? but at the same time, Madam has been with his partner for almost a year longer.... so surely that would make them more family than the previous....?

does the inclusion of a child bind people together to make them family? people always say "you are starting a family" when you have a child. what about marriage. is marriage the family starter? i don't know....

but i would like to?

if anyone has any thoughts or opinions... please let me know....