Cheryl Blossom's twin brother who died is named Jason Blossom. In the TV series "Riverdale," Jason Blossom's death serves as a central mystery in the first season and sets the tone for the dark and mysterious events that unfold in the town.
At the beginning of the series, Jason Blossom's body is found in the Sweetwater River, and his death remains shrouded in mystery. As the story progresses, the characters, especially Cheryl (played by Madelaine Petsch), grapple with the loss of Jason and try to uncover the truth behind his death.
The circumstances surrounding Jason's demise and the secrets of the Blossom family become significant plot points throughout the first season and continue to have an impact on the characters' lives in subsequent seasons of the show.