In supersymmetric theories there are mass and interaction matrices for the squarks and sleptons, leading to a rich flavor structure. In particular, if fermions and scalars of a given charge have mass matrices which are not diagonalized by the same rotation, new mixing matrices occur at gaugino vertices. This may lead in general to the dangerous light family flavor changing processes unless the breaking of S U ( 2 ) F symmetry, which controls the light family sector, together with small fermion masses yields the small mass splittings of their scalar superpartners.