John McCain's Eldest Son Doug McCain Dead at 66

Doug McCain, the eldest son of late Senator John McCain, has died suddenly.

Meghan McCain confirmed the news Sunday, though the cause of death has not been made public.

Meghan paid tribute to her brother in an emotional message shared online ... writing ... "I am deeply saddened to share the news of my brother Doug McCain’s sudden passing."

She called Doug "a truly wonderful, joyful man" and said he brought "humor, fun and great conversation to every room." Meghan added she would always cherish their memories together.

Doug was part of the well-known McCain military family legacy and served as a Navy pilot for years. He was the son of Carol Shepp, John's first wife, and was later adopted by the late Arizona senator after the couple married in 1965.

He is survived by his wife, Ashley, children Caroline and Shepp, daughters-in-law Ellie and Emily, his grandson Teddy, his mother Carol, and many others from the McCain family.

John McCain, the longtime Arizona senator and 2008 Republican presidential nominee, died in 2018 following a battle with brain cancer.

Doug was 66.