Douglas Shepp McCain, the eldest son of late Sen. John McCain, has died. He was 66.

An online obituary said Douglas died “suddenly” on Wednesday, May 20. His sister, Meghan McCain, confirmed the news in an emotional Instagram post shared Saturday, May 23.

“I am deeply saddened to share the news of my brother Doug McCain’s sudden passing. He was a truly wonderful, joyful man who supported me throughout my life. He brought humor, fun and great conversation to every room. I will cherish our memories together. Our prayers are with his wife Ashley and children Caroline and Shepp.”

According to People, Douglas was the eldest son of Carol McCain, John McCain’s first wife, from a previous marriage. John later adopted Douglas and his brother, Andrew McCain, after marrying Carol in 1965. The couple later welcomed a daughter, Sidney.

After Carol and John divorced, the longtime Arizona senator married Cindy McCain. Together, they had four children: Meghan McCain, John “Jack” McCain, James McCain and Bridget McCain.

Born in Pensacola, Florida, Douglas was raised in Jacksonville and attended Jacksonville Episcopal High School before graduating from the University of Virginia in 1982 with a degree in Systems Engineering. It was there that he met his wife, Ashley.

Douglas later served in the Navy and went on to become a captain for American Airlines, according to his obituary. Though he largely stayed out of the public eye, he occasionally supported his father during political campaigns.

A memorial gathering is scheduled for Saturday, May 30, at Princess Anne Country Club. In lieu of flowers, the family asked that donations be made in Douglas’ memory to Jacksonville Episcopal High School, the University of Virginia or a charity of the donor’s choice.

Douglas is survived by his wife, Ashley, their daughter Caroline, son Douglas Shepp McCain Jr., and grandson Teddy.