What is the ruling on a son's feeling of alienation towards his mother who treats him harshly and prefers his siblings and their wives over him, despite his dutifulness and service to her?

You must honor your mother and treat her kindly, and it is not permissible to abandon her or stop visiting her without a valid excuse, for the right of the mother is great. If there is no real harm in visiting her, then it is obligatory for you to visit her. As for a weakening of love or hatred, if it does not lead to neglect of her rights, then there is no blame in it, for love and hatred are beyond human will. However, one should not be affected by them except to the extent of the Shariah ruling. Responding to evil with good brings affection, "And not equal are the good deed and the bad. Repel [evil] with that which is better; then behold, he between whom and you was enmity [will become] as though he was a devoted friend."