The idea that a couple is automatically considered legally married after living together for a certain number of years is a common misconception. In reality, the concept of a "common law marriage" varies by state, and some states do not recognize it at all. In the United States, there are a few states that recognize common law marriage. However, they each have their own specific requirements. Even in those states, the length of time that a couple must live together to be considered legally married can vary.