I too have traced my ancestry to Patrick Dempsey. Via William, James, Edward Vincent, my grandfather James Ernest and my father Bernard Norbert. Unfortunately the trail stalls out at Patrick.

Unfortunately I know very little about my father or his family. All of my ancestors I've traced through ancestry.com. I've sent away DNA samples to 2 different companies and I look forward to the results.

After two years of exhausting searches, I gave up trying to find records of Patrick Dempsey and his wife Bridget Sinnott (or Synott) William was my 4x Great Grandfather, James, my 3X, John Patrick my 2X and John my Grandfather.  I went through thousands of birth, marriage, death records that wee in Family Search to no avail.  I read that because The Church of Castle Ellis was a civic church that they did not keep records.