Thank you! Frank's was a very sad childhood. You're right, he almost certainly never knew his father.
On his Washington D.C. birth certificate (no. 296351), Edward Fred Morris was listed as his father, and his mother, Thelma Marie Phillips, claimed to have married "Eddie" a few months prior. Her claim was supported by a May 1926 marriage license notification in the Evening Star newspaper. The marriage ended shortly after Frank's birth, and I can find next to no information about Edward Morris leading up to or beyond 1926.
At the time of Frank's birth, Thelma admitted that Franklin Thomas Tonker was Frank's biological father, stemming from a brief affair. There is no proof to this other than that she would stand to gain nothing from the claim. Frank Morris certainly would not have known Frank Tonker, and I personally doubt that Tonker would have known anything about Frank Morris. Tonker died in 1966 in a murder-suicide.
Frank did know his mother when he was a young child, despite the fact that he was seized from her at about 8 months old. She would visit him fairly regularly at his numerous foster homes & institutions up until he was about 9 years old.
Beyond his parents, Frank had contact with his biological family through Edna Irene Ellison, Thelma's first cousin on her father Milton's side of the family. Edna occasionally fostered Frank, as well as Thelma when she was a child, and was listed as his next of kin on his WWII draft registration.
I have built out Thelma Phillips' family tree and Frank Tonker's family tree, and have been able to find a very good amount of information about them in various newspaper archives & genealogical resources, but Edward Fred Morris has been a frustrating dead end. I am starting to wonder if he was only in D.C. very temporarily, or perhaps was using some kind of alias.