Conrad Bain has died.
The actor, who played single dad Mr. Drummond on Diff'rent Strokes, passed away Monday at his home in Livermore, Calif., of natural causes, according to his daughter, Jennifer Bain. He was 89.
Todd Bridges, ones of Bain's troubled young costars on the 1978-89 sitcom that was equal parts beloved and notorious, once recalled that the elder actor was more of a father to him than his own biological father was.
On Tuesday, Bridges said he was "deeply saddened" by Bain's death, and noted that he'd been looking forward to celebrating the actor's 90th birthday next month.
"In addition to being a positive and supportive father figure both on and off-screen, Conrad was well-loved and made going to work each day enjoyable for all of us," Bridges said in a statement to E! News. "He will be missed, but never forgotten."
Bridges, Dana Plato and Gary Coleman, the series' breakout star, each endured much-noted off-screen troubles during and not long after Diff'rent Strokes' run. Plato committed suicide at age 34 in 1999. Coleman died of a brain hemorrhage in 2010. He was 42.
As Bain's young costars would speak fondly of him—Bridges called him the "glue" of the cast—Bain returned to favor.
"I'm really indulging myself with the kids," the actor told the Associated Press in 1979. "I guess that's the way with grandfathers—you can have fun with them."
On Strokes, Bain was the patriarch to a pre-Modern Family clan: a white father with a birth daughter (Plato) and two adopted African-American sons (Bridges and Coleman).
Before Diff'rent Strokes, Bain put his patrician looks to good use as the stuffed-shirt neighbor on All in the Family spinoff, Maude, starring Bea Arthur.
Born Feb. 4, 1923, in Canada, Bain remained a prime-time fixture after Strokes ended. In the late 1980s, he costarred alongside George C. Scott in the early Fox sitcom, Mr. President.
He is survived by his children, Jennifer, Mark and Kent.
—Additional reporting by Marcus Mulick