According to customary law in several regions of Indonesia regarding child adoption, an adopted child has the same legal consequences as a biological child. This includes the right to inherit the wealth left by the adoptive parents. When an individual adopts another person's child, the relationship with the biological parents is severed, and the adopted child is ascribed to the adoptive parents. Based on this issue, the author aims to examine the perspective of Ibn Kathir in his exegesis of the Qur'an, Tafsir Al-Qur'an Al-'Azhim, since this interpretation is widely recognized in Indonesia and provides comprehensive explanations. From the aforementioned background, the research problem formulation was found, which discusses the genealogical relationship of adopted children in adoptive families according to Ibn Kathir in Tafsir Al-Qur'an Al-'Azhim and the inheritance rights of adopted children in adoptive families according to Ibn Kathir in Tafsir Al-Qur'an Al-'Azhim. This research is a library research, and the type of data used is qualitative data. The conclusions of this study are, firstly, that the relationship of adopted children in adoptive families according to Ibn Kathir is that adopted children are ascribed to their respective biological fathers and not to their adoptive fathers. Additionally, adopted children are not considered mahram within the adoptive family unless they have been breastfed by the adoptive mother, thus becoming mahram through breastfeeding. Secondly, regarding the inheritance rights of adopted children in adoptive families according to Ibn Kathir's interpretation, adopted children are not included as heirs in the adoptive family. However, they remain heirs within their biological family.