What? Animal Crossing doesn't let you do anything of the sort.
I'm sorry but you really ought to not think too much about some crazy wacky Japanese game that they decided to localize. The game was already made and done, what did you expect them to do, add that in specifically for the American release?
In Japan, there's not much demand for it, but if you want it in the next game maybe you could write to them (if the game doesn't flop in America). But it's probably not a priority from the creators of Wario Ware and Rythm Heaven making another silly game, not a life simulator (despite being advertised that way). No one's life is like this.
Actually, they've already changed the game to add in new things to specifically appeal to American audiences by including rap battles, which is certainly working to get me to purchase the game! No reason they couldn't also add in same-sex marriage options to appeal to even more Americans, with the added bonus of being a solid thing to do anyways.