Larry, I have tried to find your grandparents and father in the 1920 and 1930 census in Westmoreland Co, PA. The closest I could get was a John and Mary Mazur in Vandergrift township, 1920 who had a son, Joseph,age 1 10/12 born in PA. There were also other older children in this family. John immigrated in 1900 and Mary in 1903. He was a coal miner.
In the 1930 census, Monessen borough, Westmoreland Co. was a Joseph and Rose Mazur with a son, Joseph Jr. age 13 and seven other children. What impressed me was how many Mazurs there were in that county! I guess they were all working for the coal mines? I looked at every Anna, John and Joseph and I looked at every family in Monessen in 1930, convinced I'd find them under other names or nicknames but no such luck. Is it possible they were living someplace else when Joseph was young?