Ozzy Osbourne has been undergoing treatment for Parkinson's disease while also battling emphysema. Elton has been among the well-wishers.
The 71-year-old told GQ that each week the piano player calls his wife, Sharon, to see how he's doing.
''He has become a family friend,'' he says.
Osbourne was virtually presented with the Lifetime Achievement Award at GQ's Men of the Year Awards on Thursday. Earlier this year, his album, Ordinary Man, was released, and Elton was featured on the title track.