A fundamental challenge in Islamic family law is determining whether the sanctities of marriage (affinity) persist after the dissolution of the marital bond through divorce, annulment, or death. This study aims to examine the Quranic and jurisprudential evidence regarding the continuity of affinity (mahramiyat) concerning in-laws (e.g., mother-in-law and father-in-law) following the severance of the marital relationship. Specifically, it addresses whether the dissolution of marriage nullifies these sanctities or if they possess an enduring nature. Employing an analytical-ijtihadi method, the research analyzes Quranic verses of rulings (Ayat al-Ahkam), jurisprudential texts from both Imamiyah and Sunni schools, and authentic narrations. The findings demonstrate that a valid marriage contract (permanent or temporary) establishes an eternal sanctity of affinity, as evidenced by the implications of Surah An-Nisa (verses 23-24) and Surah An-Nur (verse 31). The study concludes that the dissolution of marriage—whether via divorce or death—does not terminate these sanctities, a view supported by the consensus of jurists. Beyond legal implications, the continuity of these rules serves to protect familial sanctity, uphold the dignity of causal relatives, and strengthen the moral, psychological, and social foundations of the family institution.