It depends really on how serious it was. Personally I would not care if any member of my family dated and ex of mine simply because I am happily married to the person I am with they are all in the past so none of that matters there is no residual feelings. The only person I would be mildly "uncomfortable" not even mad or upset about with a family member dating would be my ex fiancee we were together for 4 years and I lost my virginity to him other then that I really wouldn't care.
Quoting MommaSav2:" <blockquote><b>Quoting S U Z I E:</b>" <blockquote><b>Quoting A&J. ♥:</b>" ... [snip!] ... ex husband... we've been together for 13 years so probably lol..."</blockquote> There has to be a story there! Lol"