Is obedience to one's father obligatory if he commands a sin, such as severing ties of kinship or forbidding visits to uncles, and are the children sinful in this case?

The right of a father is great, and obeying him, honoring him, and being good to him are obligatory upon you. This obligation does not cease even if he is a disbeliever, so how much more so when he is a Muslim who has fallen into some sins and errors? Be obedient and humble towards him.