What is the ruling on a son boycotting his parents because they refuse his marriage to a specific girl?

If the girl is religious and of good character, her family should not reject her. However, if she is not, then they have done well in advising your brother. His estrangement from his parents and siblings is not permissible. He must uphold ties of kinship, especially with his parents. The family's rejection is usually for a valid reason. The ruling on obeying parents regarding refraining from marrying a specific woman has been previously explained in Fatwa no. 59060.