I don't know how much of this is new information for you and keep in mind that it may not be complete, but here we go: As far as Daniel's siblings go, Stephen Charles married Agnes McCormick and had three children: Agnes, married Leo Iacomini; James C, married Hilda Laehr; and Charles. Margaret married Bartholomew Brennan and had one child, Patricia. I think Mary died young. Elizabeth married Leo T. Beck and had 7 children. Agnes died unmarried of TB in 1920. I don't know any additional information about Daniel and his first wife's children but I believe the first wife's last name was Neid.
John J. Breen and Ellen McGowan were of Irish heritage but John was born in Ohio and Ellen in New Jersey. John's parents, who I also descend from, were Patrick Breen and Mary Ann O'Neil. Patrick was born in about 1835 (his gravestone says 1840) in Ireland. His father, whose name was also Patrick, died when the son was six years old and soon after, the mother and children came to America, settling in Xenia, Ohio. Patrick had a sibling named James, of which I know very litte, and may have also had one named David, who married a Catherine Agar and moved to Edgar/Vermillion County, Illinois. Patrick went to Akron to work in the Austin Powder Mill. Patrick married Mary Ann O'Neil in 1857 and had three children: James Patrick, from whom I descend; Lydia (who married Harvey Sharpe); and John J.
Patrick died in 1865 in an explosion at the mill. Mary Ann married James Glennen and died in about 1872. By the way, Mary Ann's father was John O'Neil and her mother was Mary Ann McBride.
In your note you mentoin that John and Ellen may have been from Galway. I wish I knew for certain where his parents came from but sources have pointed to either Kerry or Clare but nothing is definitive. If you've got anything pointing to Galway, I'd be interested to find out what it is.
Hope this helps!