LOS ANGELES (AP) — 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 the social platform X on 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.

“Michael was called home to be with the Lord on Sunday, January 4th, surrounded by his entire family,” his wife, Colleen Reagan, and two children, Cameron Reagan and Ashley Reagan Dunster, wrote in a statement. “Our hearts are deeply broken as we grieve the loss of a man who meant so much to all who knew and loved him.”

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

Born to Irene Flaugher in 1945, Reagan was 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, playing in television shows including “Falcon Crest,” and he spent nearly two decades as a conservative radio talk show host, speaking of politics and culture.

In two autobiographical books titled “On the Outside Looking in” and “Twice Adopted,” he told of, at times, a difficult childhood, which included coming to terms with his adoption and his journey of faith.

Reagan penned several others, including “Lessons My Father Taught Me” published in 2016, where he detailed lessons learned growing up the son of Ronald Reagan.

Throughout his life, Reagan raised money and worked for charities, using powerboat racing as a means of fundraising for the Juvenile Diabetes Research Foundation, Cystic Fibrosis Foundation and Statue of Liberty Restoration Fund. Reagan sat on the advisory board for Mixed Roots Foundation, which focuses on the foster care and adoption in the U.S. and globally.

Reagan served as chair of the John Douglas French Alzheimer’s Foundation board for three years, working on the same disease his father succumbed to in 2004.

As president and chair of the Reagan Legacy Foundation, he championed the legacy of his father. The conservative former president was known for trying to scale back government and devoting his presidency to winning the Cold War.