I believe I have information on your family (and mine).William Oldfield born 1839, Ireland, married Mary O'Brien in NY, Children: Ellen, b Jun 1870,Eliza (Elizabeth) 1872,George Mar.1875, Anna Mar 1877, John Dec. 1879, Agnes Feb 1882, Lucy Apr 1884, Harriet (Hattie) Oct 1886.MY Grandmother was Anna Oldfield Hogan.
I know a lot about the earlier O'Briens, some about the elder William, and what happened to most of them. John was widowed and living with Mary in 1920. He arranged Mary's funeral in 1928 (Calvary Cemetery), I really haven't tried to trace him beyond that. I would gladly compare notes.
(George fell under a train at the Borough Hall subway station in Brooklyn in 1945.)