They were close friends and worked together on many films and television shows, often playing romantic interests. Their on-screen chemistry was so strong that many people believed they were actually dating, but they always maintained that their relationship was strictly professional.
Annette Funicello was married to Jack Gilardi from 1963 to 1981 and later to Glen Holt from 1986 until her death in 2013. Frankie Avalon was married to his wife, Kathryn, since 1962.