I have the OH Supplemental Index from 1940-1958 and I ran a search for a Bob/Robert who was born 6-26-1942 and found one but he was born in Dayton.
That is why I asked if the OBC stated your mother was a twin.
So sorry. I wondered if they were legally adopted out or just given to someone but if your mother has her A-papers then she was legally adopted. Unknown about him?
Blessings
Mackie