What is the ruling on shunning a brother who commits grave sins and does not respond to advice, taking into consideration the parents' concern for him and their distress over his misdeeds?

The brother should be advised kindly, enjoined from evil, and prayed for guidance. If he does not respond, he should be boycotted if such a boycott would lead him to abandon the sin; otherwise, he should not be boycotted. The parents should advise and admonish him in the best manner. What also helps him towards guidance is keeping company with the righteous and assisting him in maintaining prayer.