Should one maintain or sever ties with the family of a sister's husband, if that family intermarried with the Ahmadiyya Community?

Ahmadiyya is considered a sect outside of Islam because it claims that Mirza Ghulam Ahmad al-Hindi is a prophet who received revelation, and this contradicts the consensus of Muslim scholars that Prophet Muhammad, peace and blessings be upon him, is the Seal of the Prophets.

Based on this, it is not permissible for a Muslim woman to marry an Ahmadi man, as he is considered a disbeliever. Allah Almighty has forbidden the marriage of a Muslim woman to a polytheist, as stated in the Holy Quran.

Anyone aware of this invalid marriage must inform the concerned parties of the Islamic ruling. If they do not respond after being informed, it is permissible to shun them for the sake of Allah, as a form of rebuke and denunciation of their action. The Islamic benefit should be considered in shunning; if shunning leads to a greater harm, it is not prescribed, but if it leads to deterring evil, then it is prescribed.