The son of thy mother This is added, to restrain the signification of the word brother, which is often used generally for one near akin, and to express the nearness of the relation, the mother's side being usually the ground of the most fervent affection. Thy daughter Thy piety must overcome both thy affection and thy compassion to the weaker sex. The father and mother are here omitted, because they are sufficiently contained in the former examples.
Related Commentaries of Deuteronomy 13:6
Deuteronomy 13:6
6 If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, which is as thine own soul, entice thee secretly, saying, Let us go and serve other gods, which thou hast not known, thou, nor thy fathers;