In the documentary, aired by German channel ProSieben, the man claiming to be Joseph Moukoko reportedly confessed to falsifying documents to present the striker - currently on loan at Nice - as his son and reduce his official age.
He said, via beIN Sports: "We did it so he could have better opportunities in European football."
The publication adds these revelations could suggest he exceeded the age limit in youth competitions, including Germany's Under-21 European Championship triumph in 2021. The veracity of the documentary is yet to be revealed, however.