I dont know if they is a good "Personal" question. This would depend on the relationship you have with the person you want to know something personal about. If its a boss or coworker, curb your interest. Unless, they want to fess up something, then that is intrusive. If its a new beau or gal, then that needs to wait until you are both sharing personal things, this way one doesnt fill as though the other is prying or vunerable. If its someone you just met, again, you must wait until you hit that point in the relationship when asking personal questions is not seen as a rude intrusion. You have to use your judgement. Be prepared if you stick out the arm of curiousity it may get cut off...