Caroline Corey's son and daughter were pupils at an international school in Venezuela and were taught by paedophile William Vahey.
Neither were victims, but it is believed Vahey had scores of victims across the world.
Ms Corey told ITV News: "This man, who was a friend from to me, not only groomed our children but he groomed us as parents to trust him...It really is devastating."
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His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."
The company’s recently appointed Chief Executive Dara Khosrowshahi said the breach was made by two individuals outside the company.