I'm trying to find the title of a book I read in high school. It's about a man who kidnaps the child of another man whose brother was kidnapped by the first man's father. In the end, it is revealed that the first man is actually the uncle of the child he kidnaps. His kidnapper's child died and he was raised as his son instead. This book was a paperback and not very long. It would have been published before 1985.