Tom, I have not been able to find Thomas and Emma on the 1900 census. Emma's death date in 1930 on the Minnesota Death Certificate Index is not far from Julia's in 1919, and it would be reasonable that they were of the same generation. I found reference to the older Thomas on the 1890 Veteran Schedule as enlisted in 1864 and discharged in 1865, and living in Castle Rock, Dakota County, MN. and of a Thomas Nacey living in Clinton County, Iowa in Clinton Ward 4 in 1870, but I have not seen the films on that as yet, so don't know how old that Thomas was. There were two Thomas Naceys in PA in 1900, a father and son, but from the social security records, it sounded like they stayed there.
By 1900, Patrick and Julia had 14 children, with 10 living and 8 of them listed as living with them in Duluth: Mary, Patrick F, John, Julia, Agnes, Joseph E, Charles, Edward, and Clarence. They did have a 22 yr old nephew living with them too, named John Griffin, who was born in Illinois and was working as a bricklayer. From what I have seen from obituaries, etc, Mary was married to a man whose last name was Walsh, but I don't know their address. Do you know when she died? The 1880 census listed her birthdate as 1874, and I found a birth listing for her in Ramsey County, Feb. 6, 1874.
I have been looking at this family tree because my daughter's paternal grandmother was Pearl Nacey, who was the daughter of Patrick and Julia's son, Joseph E Nacey. They lived in Cleveland. It has been an interesting search.