What is the term for two unrelated adults of the opposite sex sharing the same living quarters?

The term for two unrelated adults of the opposite sex sharing the same living quarters is "cohabitants." This term specifically refers to individuals who live together in a domestic partnership without being married, often forming a close personal relationship. Cohabitation can happen for various reasons, such as economic benefits, companionship, or convenience, and it is increasingly common in contemporary society.

The other options do not accurately describe this situation. "Demographic" relates to statistical data about populations, such as age, race, or income, and does not pertain to personal living arrangements. "Memorial Service" refers to a gathering held to honor someone who has passed away, while "Culture Universal" refers to elements, practices, or ideas that are common across all cultures. Thus, these terms do not fit the context of two unrelated adults living together.