Has he ordered the death certificate? He can get a copy from the state archives:
1946 Orleans Parish Death Records
Page: 1035 Volume: 222
That might yield some information on Solomon's parents.
According to Solomon's memorial on Find a Grave, his mother was Louisiana Gobert. tinyurl.com/SolomonGobert
As Ella & Solomon are both buried in St. Ann Cemetery, I would think he should check with St. Ann Church to see if they have any information on the family.