He's attempting to keep all of his options open.
I used to watch a show called Nash Bridges starring Don Johnson and Cheech Marin. Don Johnson's character on the show had a habit of calling every guy he ran into "Bubba," and every female he ran into "sis" or "sister." It was just a verbal habit, like some people say "man" or "dude" a lot or they say "whatever."<br />
Don't read too much into it. If your x is asking about your relationship status a lot, it means he would like to get back together with you. Otherwise, why would he care one way or another?
you should not have dated your brother?<br />
tbh it probably means they are interested but not so much as to make a move, more to make sure you are available as a backup.