In 1940 your father’s sister Garnett and their aunt Edna Martin (sister to Mary Estelle who married Joseph Jess Jones) are living next door to Joseph J Jones age 34, and Mary E Jones age 37, and son (adopted son) Robert L Jones age 9 (your father). You can see the original census image on Family Search (a free website, as you may indeed know).
Edna is widowed and living with her mother, Maggie Justin.
1940 Red Fork Township, Tulsa, Oklahoma Maggie Justin 55, widowed, born about 1885 in Missouri Edna Martin 33, daughter, widowed, born about 1907 in Missouri Garnett Martin 13, granddaughter, born about 1927 in Oklahoma Dorothy Probis 10, niece, born about 1930 in Missouri James W Probis 6, nephew, born about 1934 in Missouri Calvin Probis 2, nephew, born about 1938 in Missouri RESIDENCE in 1935 (a question on the 1940 census) Rural Tulsa County, Oklahoma (for all)
I suspect I’m finding information you already have but didn‘t share. It’s hard to know what all to include in your query and posts, I know. In general you should mention information that appears on public records: dates of birth, places of birth, middle names, surnames, and places where people were born, lived, and died.You seem to continue to avoid doing this. (For example, you mention Carrie's uncle as a possible player in this quest, but do not give his name!) Not sure if that‘s intentional, but if not, maybe it can help you if I point out the pattern of omissions. I don’t mean to intrude, or to ask you to share information you wish not to share, just saying that the type of information I mention is essential to answering genealogy questions.
Okay, now I'll look for Carrie Groseclose and Ben Shipp. When I find them, though, that will not prove who is or is not a biological father to your father. Your father's birth certificate would be the closest thing you can get to "proof." After that, a DNA test would be needed, which Ibelieve could be conducted with a male descendant of a brother to Ben Shipp (if Ben had no sons, as you say).
You mention "one of Grandma Carrie's husbands was a possible uncle to Grandma Mary." Do you have the names etc. of all her husbands?