Remus John Lupin is a character in the Harry Potter series of books by J.K. Rowling. He is first introduced to us as a teacher in the third book, Harry Potter and the Prisoner of Azkaban, when he is hired to teach Defence Against the Dark Arts. When we first meet him he is down-at-heel, even scruffy, tired, and kind. He banishes Dementors from the Hogwarts Express, and through the course of the book shows Harry how to combat them himself. He is shown as brave and intelligent, a good teacher with a natural rapport with children. For some reason, however, Professor Snape takes an apparently immediate dislike to him.
In Harry Potter and the Deathly Hallows, he marries Nymphadora Tonks, a Metamorphmagus, the daughter of Andromeda and Ted Tonks, second cousin of Sirius Black and third cousin of Draco Malfoy. Nymphadora, more often known as Tonks, bears him a son, Teddy Lupin. Both Remus and Tonks are, tragically, slain in the final battle at Hogwarts.
In the epilogue to Harry Potter and the Deathly Hallows (which many HP fans, and particularly rabid shippers with ideas that do not fall in line with those of J.K. Rowling, are attempting to ignore, but which should technically be acknowledged as canon seeing as it was published), Teddy Lupin is found snogging Victorie, the eldest daughter of Bill and Fleur Weasley. Ginny Potter (née Weasley) immediately jumps to the conclusion that they will wed.
Remus is one half of one of the most popular slash pairings in Harry Potter, Remus/Sirius Black. Thus, his death at the end of Deathly Hallows was met by a lot of slashers with a cry of 'at last! Remus and Sirius are together again!'