There is a World War I Draft registration card for Cleveland's younger brother, Sumner Musser Karstetter. On it he says he was born in Woodward, Pennsylvania,which is in Centre Co., so that might be a good place to start looking for records. There are census records for the brothers in Montana, but I didn't see any in Pennsylvania. That could mean you should also be looking for Cleve under one of the many spelling variations of the surname: Kerstetter, Carstetter, Castrator, etc.
My interest in this is that a Karstetter married the sister of one of my Whiting ancestors. The sister's brother was my ggrandfather, married to a Vonada/Vonado. Two Vonada brothers also ended up in Montana. These people were all from Centre and Clinton counties, PA.