NEW YORK -- Conrad Bain, the Canadian-born actor who played the kindly white adoptive father of two African-American brothers on the '80s sitcom "Diff'rent Strokes," has died.

He was 89.

Bain died Monday of natural causes in Livermore, Calif., according to his daughter, Jennifer Bain.

"He was very, very dedicated.... A very, very good actor," Jack Merigold, a former stage manager who was friends with Bain on the theatre scene, said in a telephone interview from his Toronto home on Wednesday.

Merigold pointed to the time he and Bain worked a 1957 production of "The Makropoulos Secret" at the Phoenix Repertory Theatre in New York City.

Bain was "quite sick" with the flu but refused to take a night off.

"There was a flu epidemic like there is now and he didn't have to leave the performance. He stayed on and performed every night," said Merigold, former assistant to renowned theatre director Tyrone Guthrie.

The show that made Bain 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 theatre actor, proved an ideal straight man. The series lasted six seasons on NBC and two on ABC.

"I never did anything with him where he had a sense of humour, and here he was doing comedy. So it shows you what an accomplished actor he was," said Merigold.

Conrad Stafford Bain -- whose identical twin brother is Bonar Bain -- attended high school in Calgary, deciding on his life's work after an appearance as the stage manager in a high school production of "Our Town."

A native of Lethbridge, Alta., Bain arrived in New York in 1948 after serving in the Canadian Forces during the Second World War. 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.

In 1958, he performed at the Stratford Festival in southwestern Ontario, in productions of "The First Part of Henry IV" (playing Northumberland and Sheriff), "Much Ado About Nothing" (playing Antonio), and "The Winter's Tale" (playing Antigonus).

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 the comedy "Maude."

"He paid his dues as an actor," said Merigold.

During the heyday for "Diff'rent Strokes," 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 "Maude," which aired on CBS from 1972 to 1978.

As Dr. Arthur Harmon, the conservative neighbour 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," he said. "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."

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