Its simple sweety,even in female pairs,one of them is called Father
How about the omegaverse where omega gives birth while having an alpha female partner? Has nothing to do with gender.
I understand some people are uncomfortable about it.
But when male omega are called Mama/Mom/Mother in a manga, it gives me that "gender roles can go fuck off" kind of feels and I love it. Tho maybe that's just me. Haha.
Mother is used for women,it just emphasises that the bottom is a "girl"
I love that everyone's okay with men getting pregnant and giving birth, but once they're being called "mother" it's too weird and shouldn't be done.