"That '70s Show" and its spinoff, "That '90s Show," focus on the Forman family and their relationships with each other. The original series aired from 1998 to 2006 and was set in the 1970s, while the sequel is set in the 1990s. Both shows feature the dynamics of the Forman family as a highlight, with Red and Kitty as the main characters. The original series had more family members, but the sequel mainly includes Red, Kitty, and Leia. The article also introduces other characters like Bernice Forman, Red's mother, and Marty Forman, Red's brother.