An adopted son has no share in the inheritance
6-1-2014 | IslamWeb
Question:
Assalaamu ‘Alaykum; Please calculate the inheritance according to the following information -Does the deceased have male relatives who are entitled to inherit: (A full brother) Number 1 (A nephew from a full brother) Number 61 -Does the deceased have female relatives who are entitled to inherit : (A full sister) Number 1 - The will which the deceased left behind and that is related to his inheritance is : it is not written will. but he did mention to his wife that he will let his wife and his adopted son to share his bungalow equally - Additional information : deceased have adopted son, but the son is actually his nephew... what is the position of the adopted son? can he inherit?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His Slave and Messenger.
First of all, concerning the heirs, the questioner said that the number of nephews from a full-brother is 61, yet there is only one full-brother. This is a very rare case (to be from one father) but not impossible. In addition, the question states that the wife claims that the deceased wanted the house to be divided equally between her and his adopted son, but you did not name the wife as one of the female heirs. Accordingly, we believe that the details of this question are incomplete and it is a hypothetical question and not based on facts. We hope that this is not the case, because we do not have time to answer hypothetical questions.
In any case, we can say in short that the adopted son is not entitled to receive inheritance from an 'adoptive parent', as there is no reason of lineage between them. Also, if he is a real nephew of the deceased, he is not entitled to inheritance because he is excluded by the existence of the full-brother. For more benefit, please refer to Fatwa 82371.
As regards how to divide the inheritance, then this is not possible before the heirs are unambiguously determined. However, if we assume that the heirs are only those mentioned in the question, and there is no wife or any other heir, then the inheritance should be divided between the full-sister and the full-brother; he gets two-thirds and she gets one-third.
If we assume that he had a wife and there were no other heirs, then the wife would get one-fourth of the inheritance, the full-brother would get half of the inheritance, and the full-sister would get one-fourth.
Allaah Knows best.