Feds investigating R. Kelly are about to get their hands on "physical evidence" against the singer ... courtesy of the family of one of his alleged victims.
Law enforcement sources tell TMZ ... Joycelyn Savage's parents are set to meet with federal investigators in New York to discuss matters related to 2 separate U.S. Attorney's Office probes into Kelly -- one by the Eastern District of NY, and another by the Southern District.
We're told the Savages will provide information on witnesses and those closely associated with Kelly ... AND turn over materials they refer to as "physical evidence." Our sources don't know exactly what that evidence includes.
The sources do say both federal investigations are "progressing very quickly" ... thanks to cooperation and testimony from several people, including Michael Avenatti and some of his clients.
As for what the feds could pin on Kelly -- we're told it could involve the Mann Act, which prohibits the transportation of minors across state lines for purposes of sex or debauchery.