How does one deal with a family member who practices sorcery and does not respond to attempts at persuasion to stop, which causes severe disputes in the home?

You must advise your brother and clarify the impermissibility of magic, using as evidence the Quranic verses and prophetic hadiths that condemn and prohibit magic and consider it disbelief, such as the Almighty's saying: "And Solomon did not disbelieve, but the devils disbelieved, teaching people magic" and "And the magician will not succeed wherever he goes." Every possible means should be employed to convince him, such as seeking help from people of knowledge. You should also fortify yourselves with legitimate protections, such as reciting Surat Al-Ikhlas and the two Mu'awwidhatayn, maintaining congregational prayers, enduring his harm with patience, and responding to him kindly.