Phillip is a friendly, wealthy white widower, who runs Trans-Allied, Incorporated. He was born December 3, 1931 in Manhattan, New York. (This made him Conrad Bain's junior by eight years.)

Kimberly Drummond is the only biological child and daughter of wealthy widower, Phillip Drummond (Conrad Bain). She was born on Park Avenue in New York City on October 22, 1964. Kimberly was shown as a caring, loving big sister to both Willis and Arnold, but as a wealthy, coming of age teenager, she suffered from various problems. Several such instances took place in season 6, one of which involved a two-part "very special" episode on the dangers of hitchhiking, where she was nearly a victim of sexual assault by a deranged man named Bill (Woody Eney). In another episode, no one in the family knew that she was suffering from bulimia, though she later admitted to having a Problem and agreed to seek help.

Willis James Jackson is the older brother of Arnold. He was born in Harlem on April 27, 1965. The boys' late mother was a housekeeper named Lucy, for a wealthy White man, named Phillip Drummond, and her deathbed wish was that he would take care of her two kids, and Philip Drummond officially adopted them in 1979. Willis's catch phrase is "Say what?"

Willis Jackson is a fictional character on the popular late 1970s-early 1980s television series, Diff'rent Strokes, and he was portrayed by Todd Bridges.

Phillip Drummond is a fictional character on the hit television series, Diff'rent Strokes. He was portrayed by Emmy Award-nominee and Golden Globe-winning television actor, Conrad Bain, who previously worked on the All in the Family spinoff Maude (1972–1978).

Arnold's father died in 1975, and his mother died in 1977. His mother worked as a housekeeper for a wealthy White widower, named Philip Drummond (Conrad Bain). Before her death, his mother expressed her wish for her 2 boys to be cared for by Mr. Drummond. He agreed, and in 1979, he officially adopted Willis and Arnold.

Kimberly Drummond is a fictional character on the popular television series, Diff'rent Strokes, and was portrayed by Dana Plato from 1978 until 1986, near the end of the show's eighth season.

Willis also had a girlfriend, named Charlene DuPrey, portrayed by Janet Jackson of both the television shows Good Times and Fame. Jackson appeared from the show's third season (1980–1981) until 1984, through the show's sixth season.

Phillip had dated several women, and would later get remarried to Maggie McKinney, a television aerobics instructor (played by Dixie Carter from 1983 to 1985 and Mary Ann Mobley from 1985 to 1986). Maggie subsequently introduced Sam McKinney (Danny Cooksey), her son from a previous marriage, to the family.

Bridges' role as Willis Jackson started to fade, because of casting changes in the 1984–1985 season, when Danny Cooksey was added as Sam McKinney, his and Arnold's new younger stepbrother. Bridges did not appear as often in the show's final season, though his name remained in the opening credits.