Michael Reagan, the eldest son of President Ronald Reagan and a conservative commentator, has died. He was 80.

The Ronald Reagan Presidential Foundation and Institute announced his death in a post on social media Tuesday, calling him “a steadfast guardian of his father’s legacy.”

“Michael Reagan lived a life shaped by conviction, purpose, and an abiding devotion to President Reagan’s ideals,” the foundation said.

His cause of death was not immediately announced.

Reagan was a contributor to the right-wing Newsmax television network and was known for his talk radio program, “The Michael Reagan Show.”

Reagan was born to Irene Flaugher in 1945 and adopted just hours after his birth by Ronald Reagan and his then-wife, actor Jane Wyman.

The young Reagan followed in his parents’ footsteps.

After attending Arizona State University and Los Angeles Valley College, Reagan took up acting, built his syndicated radio show and authored several books, including two about his personal journey titled “On the Outside Looking in” and “Twice Adopted.”

Throughout his life, Reagan also focused his time on several charities, raising money in powerboat racing and serving as chair of the John Douglas French Alzheimer’s Foundation board for three years.

Ronald Reagan, who was known for trying to scale back government and devoting his presidency to winning the Cold War, died in 2004 after a long battle with Alzheimer’s disease. Michael Reagan pushed his father’s ideas forward as chair of the Reagan Legacy Foundation.

Michael Reagan had two children with his second wife Colleen. (BBC)