וַיֹּאמְר֗וּ שְׁנֵ֣ים עָשָׂר֩ עֲבָדֶ֨יךָ אַחִ֧ים ׀ אֲנַ֛חְנוּ בְּנֵ֥י אִישׁ־אֶחָ֖ד בְּאֶ֣רֶץ כְּנָ֑עַן וְהִנֵּ֨ה הַקָּטֹ֤ן אֶת־אָבִ֙ינוּ֙ הַיּ֔וֹם וְהָאֶחָ֖ד אֵינֶֽנּוּ׃
Y ellos respondieron: Tus siervos somos doce hermanos, hijos de un varón en la tierra de Canaán; y he aquí el menor está hoy con nuestro padre, y otro no parece.
Mishneh Torah, Levirate Marriage and Release
Maternal brothers (ie brothers through the mother) are not considered to be brothers (except for mourning and testimony (were they will be) but) with regard to inheritance or Yibum and Chalitzah they are considered as if they were not [brothers], because you are only considered brothers from the father.