Darin believed his mother Nina was instead his elder sister and that Polly, who had raised him from birth, was his mother. In 1968, when he was 32 and considering entering politics, Nina told him the truth, reportedly devastating Darin. She refused to reveal the identity of his biological father, and kept that secret to her death in 1983.
Darin traveled with Robert F. Kennedy and worked on the politician's 1968 presidential campaign. He was with Kennedy the day he traveled to Los Angeles on June 4, 1968, for the California primary, and was at the Ambassador Hotel later that night when Kennedy was assassinated. That event, combined with learning about his true parentage, had a deep effect on Darin, who spent most of the next year living in seclusion in a trailer near Big Sur.