My Great Grandfather was Flavious Josephus Yonce. He lived in Stillwater County, Montana. It seems like your great great grandfather may be his brother. I found this information in the 1850 Federal Census. John Andrew was 1 yr old and my great great grandfather was 6 at the time. I am assuming you made a typo of John Andrew's birthdate being 1949. Would it be 1849? At the time they lived in St. Clair, Missouri. Not sure if this info concerns your ancestry as you say his father was Jerry Yonce (which may or may not be a nickname). My ancestry has Andrew John as Flavious and John Andrew's father. If you'd like to exchange info on your great great grandfather and possibly his brother Flavious Josephus Yonce please contact me. I'd be happy to share with a possible relative. Take care, Sally