What is the ruling on marriage despite the parents' objection without a legitimate Shar'i reason, and how should one deal with the parents and siblings thereafter?

The opposition of parents to their son's marriage falls into two categories: First, if they oppose the very idea of his marriage, then obedience to them in this matter is not obligatory. Second, if they ask him to not marry a specific woman, then the default is for him to prioritize obeying them, unless his heart is attached to the girl, and she is of good religious character and morals, and he fears temptation for himself. In this case, he is permitted to marry her while trying to convince his parents. He must honor and seek to please them by every means possible, and safeguard the rights of his siblings and all his relatives.