William Bannon married Mary Ann Hyland while his sister Elizabeth Bannon married Mary Ann's brother Peter Hyland. Fortunately, William and Mary Ann had a much smaller family than most of their siblings, with only 3 children: my great-grandmother Mary Ann Bannon who married my great-grandfather Charles Henry Smith, her brother James Joseph Bannon who married Elizabeth Monica "Lizzie" Kearns, and her sister Catherine R. "Kate" Bannon who married Patrick J. O'Connor.
I knew that my great-grandparents were buried in the same plot with Charles mother Mary Ann Reilly Smith, but had no idea where William Bannon and Mary Ann Hyland Bannon were buried, and originally I had no idea what happened to James Joseph Bannon or his sister Kate. But then I had a DNA match to an O'Connor, and in his tree was his ancestor Patrick married to Catherine Bannon. When I then looked at their burial site, it was in the same cemetery as my great-grandparents (Holy Sepulchre in Essex County, NJ), and in the same plot were William and Mary Ann Bannon. A major mystery solved in part due to DNA testing!
I worked on the children for James Joseph Bannon and his wife Elizabeth Monica "Lizzie" Kearns, merging together duplicates and attaching sources. I ended up with 20 sources for James and 24 for Elizabeth.
Then I worked on the children for Patrick J. O'Connor and Catherine R. "Kate" Bannon. By the time I was done, I had added all 10. Kate now had 9 sources.