In a minority of states, couples who meet certain requirements are considered married even if they never went through a legal marriage ceremony or obtained a marriage license. These common law marriages are treated just like legal marriages if the couple decides to separate—the common law spouses must divide their property and deal with custody of children just like married couples. But common law marriage is a lot less common than most people think. Only a few states allow it, and only certain couples meet the criteria. Learn the rules here.