Billy Joel says there was once "bad blood" between him and Elton John. In the second part of a new two-part HBO documentary Billy Joel: And So It Goes, the "Piano Man" singer opens up about how the "Your Song" musician's public declaration that he needed rehab caused tension between them.

And So It Goes,” the singer is opening up about some tough moments with longtime friend and tourmate Elton John.

Billy Joel acknowledged “bad blood” between himself and Elton John in the second installment of his two-part HBO documentary “Billy Joel: And So It Goes,” released Friday. Joel explained the pair’s fallout occurred after John publicly insisted he needed to go to rehab.

Billy Joel was welcomed by his parents, mom Rosalind and dad Howard, in 1949. Here's everything to know about Billy Joel's family, including his parents and siblings.

Joel, who is now two years sober, first checked into rehab in 2002 at Connecticut’s Silver Hill Hospital. He entered rehab a second time in 2005 at New York City’s Betty Ford Center at the insistence of his then-wife, cookbook author Katie Lee, who issued him an “ultimatum.”

Forgiveness is complicated. And so is self-examination. But Billy Joel, who has an inherent likability, and his loved ones seem to be well-practiced in the art of both.

And So It Goes' interviews all four of his wives and candidly examines singer's struggles with money, alcohol and critics

Billy Joel's two-parted documentary, And So It Goes, co-executive producer Steve Cohen opened up about Tom Hanks' approach towards the film.The HBO project follows Joel’s