(CNN) -- The family of a woman whose naked and bound body was found hanging in a Southern California mansion two years ago has filed a federal lawsuit accusing three people of plotting her death. The San Diego County medical examiner ruled that Rebecca Zahau committed suicide, but a lawsuit filed Friday by her mother and sister contends she was the victim of a murder plot devised by her millionaire boyfriend's brother, ex-wife and the ex-wife's twin sister. Zahau's boyfriend, Jonah Shacknai, owned the Coronado, California, vacation home where she was found dead on July 13, 2011. His 6-year-old son, Max, suffered a fall in the same home two days earlier and died in a hospital on July 16, 2011.
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The San Diego County medical examiner ruled Rebecca Zahau's death a suicide
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Zahau's family did a private investigation after officials wouldn't press criminal charges
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Lawsuit accuses boyfriend's brother, ex-wife and ex-wife's twin of plotting her death
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Zahau died two days after her boyfriend's son suffered a fatal fall in the same home
Other interviewees indicated that "Rebecca was distraught over @placeholder's injury," Nemeth said.