Sammeth, who started his own agency -- The Bill Sammeth Organization -- in 1983, passed away over the weekend from pancreatic cancer, according to his sister, Barbara.

Sammeth first got his start working in the mail room of a Hollywood PR firm -- and used the job to connect with The Osmond Brothers -- whom he later represented and helped to bring Osmondmania! to the masses at just 21 years old.

Billy's The Bill Sammeth Organization has been in existence for more than 30 years. The company's first clients included Cher, Olivia Newton-John, Joan Rivers and Adam Bowen.

Sammeth sued Rivers back in 2010, just after her win on "The Celebrity Apprentice" for defamation and owed money. Billy claimed Joan's portrayal of him as a "missing manager" in her documentary was damaging to his career. The case settled before it went to court.