...But doesn't supporting with Niles (and whoever the girl one is; don't remember) lock you out of Kana's Paralogue, and thus Kana him/herself? And Niles' daughter? Wouldn't the same apply here?
It's a problem with Fates (and technically Awakening too, but it lacked same-sex altogether); being homosexual is disincentivised due to permanently missing out on a unit or two. If kids could be gotten another way, then the issue wouldn't exist, and same-sex marriages in Fire Emblem wouldn't seem so...wasteful...to me.