I'm also looking for this fic I was sure it was called something like "Of Sire blood..." and I don't remember the end. It was an AU where there is no Drusilla. Angelus turned a young man called Alexander and he made him crazy, he is like a male Drusilla. There was also something about Willow being the reincarnation of Alexander's fiance when he was still human?
Does it ring any bells?
EDIT: FOUND! See comments