A Question of status

Ever have a friend who is dating someone and you want to know how serious it is, but don't want to ask? My oldest brother is in his mid-thirties and has never been married. He's been dating the same woman for the last year or so. But no one in our family wants to be the one to ask. I guess it is as if we think that the relationship is some sort of mirage or something. I don't know, but I'm not asking.