Courtesy: CBS

A stepsibling of 18-year-old Anna Kepner is being investigated for possible involvement in the Florida teen’s death on a Carnival cruise ship earlier this month, a law enforcement source and a person familiar with the matter told CBS News.

Kepner’s family believes her 16-year-old stepbrother is a suspect in an FBI investigation, according to court filings from a custody hearing obtained by CBS News.

In a statement, the FBI said it does not provide operational updates on its investigations except in rare circumstances.

One law enforcement source said the two may have had some kind of altercation.

Kepner was on a family vacation in the Caribbean with her father, stepmother and three stepsiblings when she was discovered dead on the Carnival Horizon as it was headed back to

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