How can one atone for stealing a brother’s money, which led to the mother being evicted and the ties of kinship being severed, further complicated by the brother’s refusal to give the inheritance?

You erred by committing what you did, and your brother erred by expelling your mother, disinheriting both of you, and accusing your mother of theft without proof.

You are obliged to repent. If your rightful inheritance is equal to or greater than what you took, then do not return it. Do not let what your brother did sever your kinship with him; rather, maintain ties with him and demand your right. If he refuses, resort to the judiciary. Inform your brother that you were the one who took the money; perhaps that will rectify his stance. Ask for forgiveness from your mother for causing her significant harm.