Nancy Reagan, the former actress who was fiercely protective of husband Ronald Reagan through a Hollywood career, eight years in the White House, an assassination attempt and her husband's Alzheimer's disease, died on Sunday at age 94, the Reagan library said.
Michael Reagan said on Twitter he was saddened by his stepmother's death.
"She is once again with the man she loved," he wrote.
Reagan became one of the most influential first ladies in U.S. history during her Republican husband's presidency from 1981 to 1989.
After her husband developed Alzheimer's disease, she became an advocate for discovering a cure.