The relative of the Osbourne family who has HIV has revealed himself as Kelly's cousin Terry Longden, reports DigitalSpy.
Last month Kelly revealed that "a member of her family" suffered from the condition.
Longden was at the event when Kelly made the comment but he waa not on stage.
He gave Kelly to permission to talk about it.
He told Starpulse magazine: "I told her to say whatever she wanted because it might help someone in a similar situation, but I didn't expect her to cry. I felt quite guilty. She gave me a big hug when she came off.
"I spoke to Sharon and she was fantastic," added Longden, who once appeared in reality series The Salon. "She totally understood and gave her support. Five minutes later Ozzy rang and he was great, which was a relief. They were amazing. I couldn't have a better family."