CONRAD BAIN, A veteran stage and film actor who became a star in middle age as the kindly adoptive father of two young  brothers in Diff’rent Strokes, has died.

Bain died on Monday of natural causes in his hometown of Livermore, California. He was 89.

The show that made him famous debuted on NBC in 1978, an era when television comedies tackled relevant social issues.

Diff’rent Strokes touched on serious themes but was known better as a family comedy that drew most of its laughs from its standout child actor, Gary Coleman.

Bain played wealthy Manhattan widower Philip Drummond, who promised his dying housekeeper he would raise her sons, played by Coleman and Todd Bridges. Race and class relations became topics on the show as much as the typical trials of growing up.

Coleman, with his sparkling eyes and perfect comic timing, became an immediate star, and Bain, with his long training as a theater actor, proved an ideal straight man.

In the show’s heyday, Bain didn’t mind being overshadowed by the focus on the show’s children. He praised Coleman and Bridges as natural talents without egos.

But “Diff’rent Strokes” is remembered mostly for its child stars’ adult troubles.

Coleman, who died in 2010, had financial and legal problems in addition to continuing ill health from the kidney disease that stunted his growth and required transplants. Bridges and Dana Plato, who played Bain’s teenage daughter, both had arrest records and drug problems, and Plato died of an overdose in 1999 at age 34.

Bain said in interviews later that he struggled to talk about his TV children’s troubled lives because of his love for them. After Bridges started to put his drug troubles behind him in the early 1990s, he told Jet magazine that Bain had become like a real father to him.

Bain went directly into Diff’rent Strokes from another comedy, “Maude,” which aired on CBS from 1972 to 1978.

As Dr. Arthur Harmon, the conservative neighbor often zinged by Bea Arthur’s liberal feminist, Bain became so convincing as a doctor that a woman once stopped him in an airport seeking medical advice.

At a nostalgia gathering in 1999, he lamented the fading of situation comedies that he said were about something.

I think they got off the track when they first hired a standup comic to do the lead. Instead of people creating real situations, you get people trying to act funny.

Before those television roles, Bain had appeared occasionally in films, including “A Lovely Way to Die,” ”Coogan’s Bluff,” ”The Anderson Tapes,” ”I Never Sang for My Father” and Woody Allen’s “Bananas.” He also played the clerk at the Collinsport Inn in the 1960s television show “Dark Shadows.”

A native of Lethbridge, Alberta, Canada, Bain arrived in New York in 1948 after serving in the Canadian army during World War II. He was still studying at the American Academy of Dramatic Arts when he acquired his first role on television’s “Studio One.”

A quick study who could play anything from Shakespeare to O’Neill, he found work in stock companies in the United States and the Bahamas, making his New York debut in 1956 as Larry Slade in “The Iceman Cometh” at the Circle in the Square.

With his plain looks and down-to-earth manner, he was always cast as a character actor.

It was an audition for a role in the 1971 film “Cold Turkey” that led Bain to TV stardom. He didn’t get the part but “Cold Turkey” director Norman Lear remembered him when he created “Maude.”

Conrad Stafford Bain attended high school in Calgary, Alberta, Canada, deciding on his life’s work after an appearance as the stage manager in a high school production of “Our Town.”

He married artist Monica Sloan in 1945. She died in 2009. He is survived by three children: Jennifer, Kent and Mark.