Kay Anderson is a central character in the anime Oh! Family, where he is portrayed as the 17-year-old eldest son of the Anderson family. He is an American teenager with distinct physical traits, including yellow or blonde hair that reaches his neck and gray eyes. As a member of the Anderson household, his family includes his father Wilfred, mother Sharon (or Sheren), his younger sister Fea (or Fee) who is 15, his other sister Tracy who is 7, and his half-brother Jonathan Allen, who is approximately five or six years old. The family dynamic is central to the story, and Kay occupies the role of the calm and suave older brother, providing a contrast to his sister Fea who is described as belligerent, idealistic, and something of a tomboy.

In terms of personality, Kay is known for being composed, smooth, and level-headed, often acting as a balancing force within the otherwise chaotic and eccentric Anderson family. One of his most defining and openly acknowledged characteristics is his homosexuality, which is a recurring element of his character and his role in the plot. This aspect of his identity is treated openly within the narrative, though it is also a source of humor and sometimes ridicule within the context of the show's comedic tone. Kay is in a relationship with a young man named Leif McGary, and this relationship is a significant part of his personal life and the story's subplots. The series explores the dynamics of this relationship, including its complexities, such as a love triangle where Leif eventually develops genuine feelings for Kay's sister, Fea. This situation creates interpersonal tension and drives much of the emotional conflict involving Kay, as his romantic life intersects directly with his family drama.

Kay's motivations are largely tied to navigating his personal identity and romantic relationships while remaining a supportive and functional member of his unconventional family. He does not resist his role as the composed elder brother and seems motivated to live his life authentically as a gay man, a theme that was notably progressive for the anime's original run in the mid-1980s. His role in the story is not that of an action-oriented protagonist but rather a key figure in the ensemble cast, where his personal life, particularly his sexuality and his relationship with Leif, serves as a major plot engine. The arrival of young Jonathan, claiming to be his father's son, and the subsequent family adjustments form the backbone of the series, but Kay's ongoing story arc about his romantic life and his acceptance within the family is equally central.

Regarding his relationships, beyond his parents and siblings, his most significant connection is with his boyfriend, Leif. This relationship is multi-layered, as Leif, who initially dates Kay, eventually finds himself attracted to Fea, leading to emotional complications for all three characters. Kay also has a minor female admirer named Mariko Segawa, who is unaware of his sexual orientation and harbors an unrequited crush on him. Within the family, Kay shares a unique bond as a protective, if unconventional, elder brother, particularly compared to his strong-willed sister Fea, with whom he often has a complex dynamic due to their overlapping romantic interests. Throughout the series, Kay shows some development as he navigates these complicated relationships, and while he faces challenges related to his identity, he remains a consistent and central presence in the Anderson household. He does not possess any superhuman or special abilities; his notable traits are his emotional maturity, his steadfastness in his identity, and his role as the calm center of his often-turbulent family.