Did you notice that in 1910 an Ollie Shirlen, 10, (age a few years off), is enumerated with James and Martha Shirlen in the same county as Ollie was in 1900?
This same James and Martha Shirlen are enumerated in 1880 on the same page as Henry Shirlen, the grandfather of Ollie. And based on the number of children born to Henry's wife per the 1900 census, there's a good chance that James was son of Henry, and possible father of Ollie.
What I don't like is the difference in ages of Ollie in the 1900 and 1910 census, but census records are often not exact. You'd need to triangulate this with other data about Ollie's birth.
If I were you, I would seek additional information about the family of James and Marth(a) Shirlen to see if you can identify any other possible links between the two families.