McCarthy, 41, said that the reports were extremely hurtful, reported People magazine.
"There is a crazy story going around that I once told my cousin, Melissa, that she would have to lose weight in order to get into show business. Nothing could be further from the truth," she said.
Although Jenny is responsible for helping the actress get her foot in the door, Melissa's success in the spotlight is a result of her own perseverance.
"When she was starting out, I was fortunate enough to be in a position to get her a job on a show I was doing, to learn the ropes and get some experience on a TV set in front of the camera and behind the scenes," she said.