There has been a series of books that I have been looking for, but for the life of me cannot remember the name.
In the two books I have read from the series (I believe the first two) there was a boy and his sister who were brought into the house of a great wizard, supposedly because of the girl's magic powers, but as it turned out she had been stealing his lives (of which he had 7) in order to cast magic. Later she left her world to be a princess in another world and causing all variety of problems for her other selves.
The other (I believe to be the second) had the wizard from the previous book as a child with 7 lives. He knew he had magic powers (I believe) and against his teacher's wishes (who also had seven lives). He met a cat princess who was supposed to be sacrificed to the cat gods and rescued her, though she was never to be sacrificed in the first place (they were going to use one of the cats in the temple).
I remember this was something that I had read as a teen (10-12 years ago) and really enjoyed it, but I have never been able to find the name of this series so that I could start buying them for myself. Can you all help me out?