I only just started to follow this thread but yeah the records are pretty overwhelming that both in 1935 and in 1940 Your dad Eugene Clarence Pronk born around 1921, NY, was living with at the very least his father Clarence Pronk born around 1886 in New Hampshire. We only really know that Maude was his wife, very easily could have been a stepmother.
In the 1910 census Clarence (your grandfather) is married to a Grace, they are no children, Clarence is still living with his parents John E, and Melissa. Both John and Melissa were born in New Hampshire
In the 1920 census Clarence shows married to a Luella (19yo) they are living with Luella's aunt and uncle, she is likely pregnant with your father Eugene Clarence at the time of the census.