I was writing an essay when I used the word morganatic and I realized I don't quite know the word for a marriage between people of unequal ranks that society holds as unfair or against the norms. it can be related to a marriage or relation and mean similar to what I described.
Traditionally, in the UK, this would have been described as an unequal marriage. This term will sound old-fashioned to an American English speaker, and probably in the UK too; then again, the concept is fairly outdated as well.
In the United States, the concern is more likely to be related to money than to social class. The derogatory term used for a woman who marries a richer man is gold-digger; the man she marries would be a sugar daddy or meal ticket. A man might be be described as a gigolo, by analogy to an actual gigolo or paid companion.
inter-class marrige should be a possibile definition.