What is the way to deal with a brother who is disobedient to his parents because of his wife, who exploits him financially and causes family problems, and attempts at reconciliation have failed?

Disobeying one's parents is one of the gravest major sins, and Allah and His Messenger have forbidden it. The disobedient child must be reminded of his transgression, admonished, and prayed for. It is permissible to boycott him if that will benefit him in returning to the straight path.