The baritone vocalist died on 26 December 2010 from undisclosed medical complications in Voorhees, New Jersey.
Wilson was part of the classic Blue Note lineup that also included lead singer Teddy Pendergrass - who died in January.
The group had a huge international hit with the songs If You Don't Know Me By Now and Don't Leave Me This Way.
The dance track The Love I Lost has been credited as one of the first disco records.
Wilson left the band in 1977, a year after Pendergrass's departure.
The singer's cousin Faith Peace-Mazzccua told the Associated Press that Wilson "left home at 16 as a pauper and came back home a millionaire".
She said her cousin kept performing until recently, adding, "He didn't take no stuff and he loved people."
