One way to hold this word: think of something that was never written down and signed, but became real anyway because it went on for a long time. Judges decide case after case, and after enough years those decisions are the rule. Two people share a home year after year, and after enough years other people speak of them as married. In both pictures, the force comes from the long run of real life, not from a document.
From the picture
住出來的婚姻關係
把「靠長期實際狀況成立」這個想法從法院搬到家裡：關係不是簽出來的，是住出來的。
adjective · B2
Used before marriage, husband, wife or partner to describe two people who are treated as married because they have lived together as a couple for a long time, even though they never had a wedding or signed any marriage papers.
同居形同婚姻的
adjective · C1
Belonging to, or based on, common law — the body of law that has grown out of judges' decisions in earlier cases, rather than out of written laws passed by a parliament or congress.
普通法的；習慣法的