Responses
(forgot which chapter, but) it's said that they aint blood-related so if anything i'm guessing that he is adopted by the old guy and she is the long lost grandchild (which she is, cause u have her parents story and they're related to the old guy - that why he was looking for them after the plane crash)
She is gonna catch him. the whole marrying the sibling thing is a bit strange and I feel it is holding the story back. they didn't have to be siblings biologically. she could have been adopted by the grandfather or brought in as a choice for a future wife (by grandpa) or maybe as a exchange student or have it where she was suppose to be seeking a man to marry or have her get lost and the people who found her are also rich.