I have a feeling relatives asks those questions more than ones family. I'm not saying you should out it for everyone at ones, definitely not, but the chances of an opportunity to talk/discuss/tell about it in a situation other than "apropo of nothing" is greater at those gatherings. I got started to talk this way, in the sense of maybe not feeling that romantic relationship with the whole package is fore me. You on on the otherhand seem much more certain, so maybe outing all the way is the way to go. Only suggesting of the possibility of could be an alternative. Best of luck!