I just met the "parents" of a friend who has THREE sets of inlaws - his original parents, each of their current spouses, and an interim step-mom who was married to his dad for a while, and when they divorced, he decided to keep the stepmom rather than the dad (dad's a jerk) and HER new husband. Introduced to me as, yes, mom and dad. Having met another, different mom and dad I was, shall we say, a mite confused. Whould that make him a step-step-dad? my former stepmom and stepstepdad? My exstepmother and step-dad once removed? PLUS, one of his wives's (he has two - don't ask) dad's decided he was gay after her mom died, so what is his parner? dadpartnerous?
Therefore, we need a whole new vocab for these kind of families. (And then there's those who are connected but not by marriage, hence my daughter's auntie (married to her father's brother) is my sister-out-law.) And my parents-out-law.) Thus, when I get invited to dinner and "mom and dad" are going to be there, it can be any of five couples. (At least if its "dad and Ralph" I know who they are talking about.)
How about dadprime, dadsecundus, dadtertius, etc? No, that doesn't account for the blood-vs-married-in. stepmomprime, stepdadsecondus, stepsisterdadsecundus, stepsisterstepstepdad. Yoicks.
"Giving away the bride, the step-step-father-out-law was radiant in morning clothes, the stepmother-twice-removed of the bride wore puce. Also in attendance were dadprime stepmother quartius, and the tertius and quartius stepchildren; dadsecundus dadpartnerous and the partnerous adult childern and their parners, including ex-parter and spouse Joneses; the bride's stepsisters, sister-outlaw twice removed and cousin-in-law twice removed made up this lovely wedding party."
Maybe I'll write to Miss Manners.