How can a person act if his parents and siblings treat him harshly and have abandoned his wife, while his father orders him to make his wife remove her niqab and not visit her family, and he fears falling into disobedience to parents if he does not obey them?

You are not obligated to obey your parents regarding your wife removing her niqab or preventing her from visiting her family. Indeed, it is not permissible for you to obey them in this matter. You should gently try to convince them. Your disagreement with them on these issues is not considered disobedience (ʿuqūq) because obedience is only in what is good (maʿrūf). You must honor them and treat them well, no matter how badly they treat you. Similarly, be keen to maintain ties with your siblings and treat them well, even if they treat you poorly. Responding to bad deeds with good ones brings affection and protects against the evil instigations of Satan.