I believe that your g-grandfather, Jack Fallin Sr. is probably John Jacob Fallin, son of Benjamin Franklin Fallin and Sarah Jane (Devore) Fallin.They were married in Vandalia, Fayette Co., IL in 1860 and had a large family before moving west to Myrtle Creek OR (Douglas Co) sometime between 1880 and 1890.Of their several children, only four survived.These were:
William Henry Fallin b. 1863 John Jacob Fallin b. ~1873 Claude Fallin b. ~1876 Susan Emily Fallin b. 1878 (*my g-grandmother)
The Fallin family can be found in the 1880 census in Fayette Co., IL, St. Elmo census place, p. 126D.Before moving to IL the Fallins lived in Bracken Co., KY.Benjamin Fallin was a physician and also served, along with several of his brothers, in the Civil War.His parents were Henry Fallin and Susan (Stroube) Fallin.His paternal grandfather was David Fallin; his maternal grandfather was Jacob Stroube.The Fallin family traces back to the eastern shore of MD - the Stroubs/Straubs to PA.
Sarah Jane Devore was the daughter of William and Emily (Newmire) Devore of Fayette Co., IL and the grandaughter of George Devore and Sarah (Luce)Devore.A number of her brothers were also Drs. in Douglas Co. OR, including Commodore Perry "Doc Perry" Devore and William Devore.Perry Devore's daughter Bertha Devore was one of the very early women physicians in the area.
Does this sound like your family?I have more if you're interested.Please also see earlier postings at this site regarding this family including #172-177, #32 and #140.