Peter Francis Patterson - County Mayo

I am searching for family of Peter Francis Patterson, born 11/17/1863 in County Mayo. Peter Francis' twin sister was name Katie. The twins were the youngest in a family of 13 children. Peter and Katie were from a Roman Catholic family. Katie met and married an American man in Ireland then he took her to Germantown Pennsylvania. She sent money to her twin Peter so that he too left Ireland and came to the United States. He immigrated to the United States between 1880 and 1883. He lived in Massachusetts for some time. He joined the U.S. Army in Boston, Mass. in 1889 and was stationed shortly thereafter in Rock Springs Wyoming. His sister also immigrated to U.S., but I don't know if at the same time. His death certificate does not list the names of his parents. Griffiths Valuations lists Pattersons in the following parishes: Ballysakeery (Cooneal), Crossmolina, Kilmoremoy, Ardaugh. The 1901 census shows that Pattersons who are Roman Catholic lived in Castlebar Urban, Caraun, Tagheen, Claremorris & Balla.