Um, really?
I'd say Fantasy's still more well-known than Age of Sigmar.
Shoo!
It's not impossible to create female Space Marines, but I've gone on length saying why I dislike the idea before, so here's the TL, DR:
-GW's already done one asspull with the Primaris marines, doing another one so close is really pushing things.*
-I'd be more sympathetic to the idea if the people pushing for female Space Marines were also pushing for male Sisters of Battle/Sisters of Silence, but no, the logic appears to be that all-male orders are a no-no, while all-female orders are fine.
-You point out, correctly, that it throws a wringer in the father/son dynamic. Could you do something interesting with a deviation from that dynamic? Absolutely. But I never see that reasoning given, the people who tend to want female Space Marines often want them for the sake of their presence, and nothing else.