They may not have a piece of paper but they are married. Common law marriages are recognized by many states.
https://en.wikipedia.org/wiki/Common-law_marriage
Common Law marriages are still recognized as valid in Colorado, Iowa, Kansas, Montana, Rhode Island, Texas, Utah, and DC.
Common law marriages are recognized by many states.
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I am reminded of a case involving actor Lee Marvin...
He got sued by a woman who lived together with him for many years...The courts did not accept her claim that he owed her financial support...
https://en.wikipedia.org/wiki/Palimony
Only seven US states and DC