Douglas “Doug” Shepp McCain, the oldest son of the late U.S. Sen. John McCain, has died at the age of 66.

The McCain Institute announced his death Saturday on social media.

“A Navy pilot like his father, Doug will be remembered as a patriot and friend to the many alumni of Sen. McCain’s Institute, campaigns & Senate staff,” the institute wrote.

His sister, Meghan McCain, also shared the news Sunday on social media.

“I am deeply saddened to share the news of my brother Doug McCain’s sudden passing,” she wrote. “He was a truly wonderful, joyful man who supported me throughout my life. He brought humor, fun and great conversation to every room.”

CBS first reported Doug McCain died suddenly on May 20. No additional details about his death have been released.

Doug McCain served in the Navy, flying A-6 Intruders for six years, before later working as a pilot for American Airlines.