What is the ruling of the Sharia regarding a father seizing his children's inheritance from their deceased mother and refusing to give them their rightful share from it, and what are the implications of this in terms of severing ties of kinship? Is it obligatory to honor him in this situation?

If a father withholds his son's rightful share from his mother's inheritance, he is unjust. It is permissible for the son to take the matter to court without this being considered an act of disobedience (ʿuqūq). However, he must continue to honor his father and treat him well, for a parent's right to dutifulness and kindness does not cease, no matter how much they might mistreat.