You have some popular last names to work with. What last name would Barbara Williams-Wilson have been using when the 1940 census was taken? Was her brother Paul already born? Were they in Cleveland?
Maybe you can find an obituary for Mammie Robinson [Buckner or Williams] in a newspaper. Sounds like she died about 1946 - was that in Cleveland? If you can find one it might name her parents or brothers & sisters.
Good luck! -NGP