What is the ruling on a father who is not just between his wives and children, and who avoids communicating with his children?

If your father does not act justly between his two wives, he is an oppressor due to his lack of justice and his severing of kinship ties by favoring some of his children over others. However, his right to dutifulness does not cease. Therefore, you must be dutiful and kind to him. Part of dutifulness is advising him gently and respectfully, or seeking help from some righteous individuals to explain the obligation of justice between his wives and to warn him of the consequences of oppression. You should not succumb to feelings of hatred towards him.