Please pardon me if this is in the wrong forum, or I end up offending anyone. That’s not my intent.
That said, I’ve wondered for a while…in families in which the parents are a same-sex couple, what’s the most common nickname that the kids use for the second “Mom” or “Dad”? (And I do realize that aside from the linguistic angle, calling either parent the “second” one would be arbitrary and meaningless, not to mention rude.)
I mean, it would be perfectly appropriate for both parents to go by “Mom” or “Dad,” but I can imagine that it could get confusing really easily.
Well, thanks for your time,
Ranchoth
I used to live next door to a lesbian couple with young kids. One of them was “mom” and the other was “momma Melissa”.
I imagine it varies. But an obvious possibility is using “Papa” and “Dad”, etc.
Well, when I was growing up I called my parents by their first names and still do. I imagine that system would pretty much solve the problem :).
A lesbian couple I know recently had twins. Well, that is to say, one of the couple actually HAD the twins. Anyway, the kids call them “Mum” and “Mummy”.
Max 
I remember the sketch on the old Tracey Ullman show of the girl with two dads … one was “my dad” and the other was “my William.”
In my sister’s house it’s “Mother Mary” and “Mom Fran.”
Really, I don’t see how the question is any more difficult than multiple grandparents (which of course happens frequently in all sorts of families). And if great-grands are still in the picture, it just gets more complicated. My niece, for instance, has three “grandmothers” (maternal, paternal, and maternal-great-maternal), and each one has a different variant of the “Gramma” title. And when I was growing up, there was no confusion between “Grandpa” (paternal side) and “Granpap” (or even “Pappy”) (maternal side).
When I’m writing a story that involves homosexual men adopting, this is the method I use. ::shrug:: It works for me. If it’s homosexual women, I’d go with “Momma” and “Mother.”