I am collecting the last few addresses for our guest list and it involves talking to some of DF's family his mother wants us to invite. I have asked DF and his mother to get these addresses for me for several months, but they haven't, so I am just going to do it myself even though I don't know them terribly well. What is a generally polite way to ask if they have a significant other we need to invite? More specifically, one of his relatives was supposed to get married this month, but the wedding was called off under some difficult circumstances. Is there a way for me to sensitively ask him if I should invite his ex-fiancée or if they are truly broken up?