I'm coming back to this thread to drop this insightful tumblr post I saw the other day:
The poster here is addressing something different from what you're talking about but I think there's something to it; blurring the line between traditionally 'platonic' relationships like mother, sister, and even friend with the 'romantic' roles of boyfriend, wife, etc is certainly something I do with my queer friends. It's not quite the same thing but I think there's something to be said about desiring a relationship with someone that is both close physically and emotionally but yet does not reach the 'level' of 'partner.' I like relationships that are as close and reliant as the sister but I also like having sex, if you get what I mean.