1. gāthin 2. vidathin 3. keśin 4. gaṇin and 5. paṇin remain unchanged before the Patronymic also.,
Thus गाथिनोऽपत्यं = गाथिनः, वैदथिनः, कैशिनः, गाणिनः, and पाणिनः ॥ This sutra applies to Patronymics.,
गाथि-विदथि-केशि-गणि-पणिनश् च
Adhyāya 6 · Pāda 4 · Rule 165