The former President and first lady's son, Ron Reagan Jr., spoke to the Today show on Monday, in the wake of his mother's death, recalling his parent's unfailing love.
"Once they had bonded together they really were inseparable. I mean, it sounds cliché," the 57-year-old said.
"I don't think that they ever spent a day a part where they didn't call, speak on the phone. He wrote her letters all her life, all his life. They were in love and they stayed in love for 52 some odd years."
Nancy died of congestive heart failure on Sunday. She was 94.
The Reagans' daughter, Patti Davis, released a statement on her website, revealing that her mother died in her sleep.
"My mother had been in poor health for quite a while, and recently had gotten markedly worse, so this wasn't a surprise," Davis, 63, wrote in the statement. "That said, death always feels like a surprise. I appreciate the attention and prayers of people I will probably never meet."
Her spokesperson said in a statement that the former first lady will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her late husband who died on June 5, 2004.
Ron Jr. said his father's death changed Nancy.
"She was lonely without him, and said as much," he said. "She missed him terribly."
Now, Nancy will rest much like she lived her life, by her husband's side.
"She loved her husband more than anything in the world and I think that you can make the case that the Ronald Reagan that we all came to know as president would not have existed without Nancy Reagan," he said.
Bill Ray / The LIFE Picture Collection / Getty
"She knew how to love somebody," he said. "And you can do a lot worse than that in life."