Keith Claes♂

Catarina's adoptive brother and an earth magic prodigy. In the game, Catarina bullied him, causing him to grow up to become a womanizer. In the good ending, he has Catarina exiled and abandons his womanizing ways to be with the protagonist, whilst the bad has him kill his sister in a fit of rage before disappearing. To avoid these endings, Catarina goes out of her way to be a good sister to him, which does improve their relationships but also saddles Keith with the thankless task of having to keep Catarina out of trouble, mostly to no avail. He also seems to be a foil to Geordo's attempts at getting closer to Catarina as he himself has feelings for her.

[from Wikipedia]