A simmering family feud has jeopardized a wrongful-death case against accused cross-dressing killer Robert Durst for the murder of his wife over three decades ago.

“My sisters have said to me . . . ‘Why are you doing this?’ They didn’t want me to pursue justice,” said James McCormack, whose youngest sister Kathleen was Durst’s first wife.

Instead, James said, his siblings want to “protect their privacy.”

Durst has been the only suspect in the disappearance and was recently caught seemingly confessing in the HBO documentary “The Jinx.”