Homer puts Achilles as a mother not as a father and brother because Achilles is being apart from war like a woman does. From generation to generation, it’s like the custom that normally a mother cares and feeds her child and a father provides security for his family. He tries to care his child- Patroclus- and lives like a normal life. In the Illiad only brothers and fathers are going to war. Achilles isolates himself like a woman does, no matter how many Achaeans die in the war or whatever is happening, he is just staying in his home, so Homer sets Achilles as a mother rather than father or anybody else.
