With remarriage (whether after death of a spouse, or after divorce) being such a major “driver” of family-like relationships in modern USAmerica, ex-stepkin, ex-kin-in-law, and stepkin-in-law, are frequently either acquired or retained “kin”. These types of fictive kin are called “quasi-kin” by some authors.
See, for example,
“[url wrote: https://psycnet.apa.org/record/1982-09679-001[/url]”] Quasi-kin relationships and marital quality in stepfather families.
and/or
“[url wrote: https://search.proquest.com/openview/5b ... 750&diss=y[/url]” Quasi-kin relationships, structural complexity, and marital quality in stepfather families: A longitudinal investigation
(Remarriage after a spouse dies, and adoption, are ways of acquiring new quasi-kin, which were fairly frequent even in earlier centuries. And I would guess that a bereaved spouse might still regard, or at least treat, their late spouse’s surviving kin as still being the living spouse’s kin; that’s a way of retaining kin as quasi-kin that saw much use in at various times in various countries in the previous 1500 years.)
I’d like to know whether there are any other natural languages than North American English in which such terms have been growing in recognition and use since around 1970 ?
And what do those natlangs call these quasi-kin?
And what about conlangs you know, or know about? Especially your own conlangs, or those on which you are or have been a collaborator?