Coming onto an FB discussion where someone casually denounced multiparent families by “there are only two parents“, I recognized the rhetoric and also how this is a more generally relevant comparison to highlight what social constructs surrounding reproduction function like in practice.
There certainly exist nonbiological parentage (star family vs nuclear family, sometimes); adoptions, explicit or implicit, bonus parents, egg donation, insemination, triads and polygons, probably a number of workable surrogacies, someone just having been around enough to be effectively a parent. We legally and socially are (mostly) able to recognize nonbiological parenthood here, just as with transitioning genders. Similarly it has long history and wide anchoring out in the world, and similarly there are also challenges, worries, fears of not being genuine.
In fact I’d argue the analogy is almost perfect, and as such is a good way of understanding how in practice we can, or do, work with these social constructs transparently in diverse lived lives throughout the world.