Hi again, Joan! Ithink you have nailed it! I found a couple of things you might be interested in:
Have you seen the Family Search Pilot Program that has the Texas Death Certificates online? Not just the index, but images of the actual documents. I found (links below) Arthur (listed as Sammual A.), with William "Buck" Robinson as his father and Mollie Mary Benson as his mother (interesting, huh?). Also found Frank as William Franklin Robinson, father William M. Robinson and mother Mary Benson. Also found Mollie...she's listed as Mary Emilia McKelny (note the 'n'--the death certificate is typed, too, and the informant is E.D. McKelny). Her father is William Robinson (and unknown mother). Of note: She's buried in Olney and it says she was born in Llano Co. Might be a hint there. She was living in Clyde (Callahan Co.) when she died in Abilene (Taylor Co.).
Also found Frank buried in Sunset cemetery in Montague Co (nearby county). He's buried with C. C. Slayton and Lois H.
You have this one nailed! Now all you have to do is find out who Sarah was! (Oh! And I think Blanche might have been a daughter in law)
Good luck! Andrea
Links: (If you have trouble opening or finding, let me know)