In World 12A, the Chants are socially respectable and noted for producing many powerful magic-users; most of the males of the family are enchanters. The family has produced at least two nine-lifed enchanters, the most powerful type of magic-user known; one of these, Christopher Chant, went on to become Chrestomanci, and the other is currently next in line for the post.
On the other hand, it is widely known that one Chant in every generation goes to the bad. Christopher's father was the black sheep of his generation, and the black sheep in the generation after Christopher appears in Charmed Life: see Charmed Life (spoilers). The black sheep of Christopher's own generation is unknown, although had things gone differently it might easily have been Christopher himself. (It seems likely that it ended up being Francis and Caroline Chant, because of the circumstances of their marriage; certainly they seem to have been on bad terms with their relatives.)
Known family tree (first generation may not be in correct order):