Mm. [She touches her left arm.] To a mage family, passing on their knowledge and spells means everything, but passing it down is a difficult process. There can only be one heir. It's customary to have only one child for this reason, or to raise any other children with little to no knowledge of magic's existence.

[Rin smiles, a little sadly.] In a freak stroke of luck, however, both my sister and I were born with above average potential.