wait so you and qrow werent dating but now you are?? how did that even happen
Consider the tired plot of a romantic comedy.
Two friends start play-acting a couple for whatever reason (the sake of their cosplay OTP, for a lame example). They do couple-y things, they joke about being a couple, they move in together, etc.
Eventually the line between acting and reality is no longer quite as visible.
There you have the full story. More or less. <3