Two of Robert F. Kennedy’s children are calling for a new investigation into their father’s assassination, opening a rift in the famous family as it prepares to commemorate the 50th anniversary of his death next Wednesday.

Kathleen Kennedy Townsend, the former lieutenant governor of Maryland, told the Globe this week that she supports a new investigation, joining her brother Robert F. Kennedy Jr., who revealed last weekend that he visited convicted assassin Sirhan Sirhan in prison and believes someone else killed RFK.

“I think Bobby makes a compelling case,” Townsend wrote in an e-mail.