The search for the family of your adopted veteran presents significant problems...even if you do acquire the IDPF.
First of all, he is an older soldier, being born in 1911. If any of his siblings were still around they would be nearly 100 years old.
Secondly, the name Martin is among the top 20 surnames in the US.With a relatively common first name and no known middle initial that makes pinning him down doubly difficult. The shortened first name can morph into Thomas, Tommie, Tommy.
Third, being a negro and living in Alabama in the early part of the 20th Century it is unlikely that he was a bank president...which might make tracking him a bit easier...but what few hits I got off the Census indicates that it is most likely that he and his family were sharecroppers, or tenant farmers. The probability is that they moved around a lot.I found an interesting possibility in Barbour County, AL, in 1920, but that is some hundreds of miles--and twenty years removed-- from Jefferson County of the 1940's.
The primary town in Jefferson County is Birmingham.This is also a key location for African-American History.You might try contacting the local historical societies to see if there is something in their archives about him.Remember, in the unlikely event that there was anything in the news paper regarding his death, it would probably appear weeks or even months after the event. Check to find out if there are African-American oriented newspapers in the Birmingham area.
Just as a side note--there are three members of the 900th QM Laundry Co. buried in Margraten--all with concurrent dates of death--something must have happened there.All three are listed DNB--Died Non-Battle.
Lastly--It looks like the 900th QM is still a going concern--maybe not specifically in the Laundry business--but the numeric designation still exists and is active.Every unit has a history section.See if you can run them down.