Red Rain by R. L. Stine
When Lea Sutter visits the Caribbean island of Chat Noir and witnesses a devastating earthquake, she is moved to adopt two beautiful, blue-eyed orphan twins, Daniel and Samuel, and take them home to America. But Lea's own children sense something strange and wrong about the boys and their innocent, oddly old-fashioned ways - and soon after they arrive, a terrible accident takes place on their doorstep. As more grisly and suspicious events take place, the boys' true origins - and their evil intentions - become terrifyingly clear.