Dusty, I believe I found Guy L. Bainter in the 1900 and 1910 census but it looks like an infirmery in 1900 and a children's home in 1910, leading me to believe he was orphaned. However, in the 1900 census there are also an Isaac Bainter, aged 42, married 1 year and a Daisy Bainter, aged 27, Single.
The census was taken in Union, Fayette which means you're probably related to either George or Henry Bender/Painter/Bender (depending on what document you read). If Guy was adopted you might have to do a little digging. I believe your grandfather Willard was born August 11, 1935 and was living in Washington Courthouse as of the early 2000s' If he is still alive and in the area, that would probably be the best place to start. Washington Court House is where all the Fayette County records would be held. Also, both George Bender, and his brother Henry from whom I descend, are buried in Fayette County in Stuckey Cemetery. I took a trip out there in 2009 during some research of my own. If the trail ends with Guy L. Bainter because he was adopted and you cannot find any records going further back, you might want to consider paying for a DNA test through one of the on line services, such as Familytreedna.com. If you are related to my branch of the Bender family, your markers will most likely come up pretty distinct from the other thus far tested lines.