Although not a legal definition these are the guidelines that the insurance policy (Blue Cross Blue Shield) in which I WAS a domestic partner followed. They were mostly concerned with verifying that we had lived together (although their requirements were that we lived together for 1 year rather than 6 months). They were also the same essential guidelines we were to follow when my husband and I looked into his policy's domestic clause (Avmed).RRevak - this is NOT a legal definition...it is not even one that insurance companies have to adhere to.