Dr. Jason Seaver (portrayed by Alan Thicke), a psychiatrist, works from home because his wife, Maggie (Joanna Kerns), has gone back to work as a reporter. Jason has to take care of the kids: ladies man Mike (Kirk Cameron), bookish honors student Carol (Tracey Gold), and rambunctious Ben (Jeremy Miller). A fourth child, Chrissy Seaver (twins Kelsey and Kirsten Dohring; Ashley Johnson), is born in October 1988. In the middle of season four (1988–89), she was first played in her infant stage by an uncredited set of twin sisters. Then, by season five (1989–90), she was played in her toddler stage by alternating twins Kristen and Kelsey Dohering. In seasons six and seven (1990–92), Chrissy's age was advanced to six years old. By the seventh and final season, homeless teen Luke Brower (Leonardo DiCaprio) is brought into the Seaver family to live with them nearly until the end of season seven.
The season one main opening features various works of art and vintage photography depicting family life, closing with a shot of the cast.
The opening credits from seasons two through five features an opening shot of the cast in front of the Seaver house exterior. This is followed by a series of photos of each cast member from their childhood onward ending with a clip from the show. The credits closed with another shot of the cast in front of the Seaver house before they all run inside. Starting in the fourth season, several different versions of the opening sequence were filmed. Whoever was the last to go into the house would usually be the focus of that week's episode.