What is the ruling on women shaking hands with and kissing non-mahram men at family gatherings, and what is the sin incurred by practicing these customs and traditions that violate Sharia in order to avoid the anger of relatives?

Customs that permit shaking hands with and kissing non-mahram (definition) men for women are invalid and contrary to Islamic law. Obedience to anyone who orders such acts, whether a husband or a father, is not permissible, as obedience is only in what is right. It is obligatory to denounce these abhorrent customs and to clarify the ruling of Islamic law concerning them, and the anger of relatives is of no consequence. A believer prioritizes the command of Allah above all else and strives to change reality that contradicts Islamic law. Allah Almighty says: "And if you disagree over anything, refer it to Allah and the Messenger." It is obligatory to abandon these customs that contradict Islamic law.