What is the ruling on exposing a married fornicator and one who commits major sins, and publicizing their actions among family members to deter them and to warn others about them?

The fornicator and other sinners should be concealed, not exposed. The Prophet, peace and blessings be upon him, said to Ma'iz: "O Hazzal! If you had covered him with your garment, it would have been better for you." And "Whoever conceals a Muslim, Allah will conceal him on the Day of Resurrection." Moreover, accusing someone of fornication requires legitimate proof, and whoever accuses a person without proof is subject to the punishment for slander. The general rule in Islamic law is to conceal Muslim sinners, except for those known for evil and corruption. In such cases, their matter should be referred to the competent authorities, and they should not be spoken about publicly, as this constitutes backbiting.