Rep: Farrah Fawcett and Ryan O'Neal Never Ended Up Marrying

Farrah Fawcett and Ryan O'Neal never ended up getting married, the actress' rep tells

In a 20/20 interview (airing tonight), O'Neal tells Barbara Walters that Fawcett "agreed" to marry him before her death.

(The two - who began dating in 1980 - have a son, Redmond, 24, who is currently serving a prison term in California after repeated drug offenses.)

"I promise you, we will," he tells Walters. "Absolutely."

Take a look back at the life of Farrah Fawcett

After Fawcett died of cancer at age 62 Thursday, O'Neal - who was by her side at Saint John's Hospital in Santa Monica, Calif. - told

"Although this is an extremely difficult time for her family and friends, we take comfort in the beautiful times that we shared with Farrah over the years and the knowledge that her life brought joy to so many people around the world."

See Us' photo tribute to other stars who have died too soon