*NSYNC Star JC Chasez's Father Dead at 73, Bandmates Attend Service

Ray "Roy" Edward Chasez, the father of JC Chasez, has died ... TMZ has learned.

Sources tell TMZ ... Roy died last month in Florida after a battle with cancer. This was his fifth bout with the disease.

We're told a celebration of life was held on Saturday in the Orlando area and multiple members of *NSYNC attended.

Our sources tell us other people from the music industry also attended the service, as they knew Roy well ... because JC’s parents, as well as the rest of the group members parents, were intricately involved in *NSYNC from the start, since at the time the guys were young.

Roy worked as an IT manager, and also as a contractor with the government ... with offices at the White House and U.S. Postal Service headquarters in Washington, D.C. We're told he worked with numerous charities over the years ... and his family was his life.

He's survived by his wife of 51 years, Karen, and his children -- JC, Heather and Tyler.

Roy was 73.