David Breen / Johanna Crone (Cronin)

I'm hoping for some guidance on how to find the male children of David Breen and Johanna Crone.  I'm trying to figure out how my husband connects to this family (long story).  Thre Breens' male children were:Patrick, Harry, Daniel and John.  Oddly enough, I've had pretty good luck finding information on the daughters, but it's the boys that I'm particularly interested in, particularly if any of them emigrated to Canada.  I haven't been able to find much, including marriages and deaths.  Hoping that someone here may be a descendent or know where to look other than the obvious on-line sources.  I'm at a complete dead end with this search.  Please and thank you!