Updated: Dec 15, 2022
As per Islamic law, there is no legal share for Adopted child or children as they can inherit from their own parents but not from the parents who have adopted them. Refer “...And he has not made your adopted sons your (true) sons....”-Holy Quran 33:4
The ruling regarding adopted children is as follows under Islamic law.
Adopted children cannot receive an inheritance.
Adopted children can receive lifetime gifts (i.e., Hiba).
Adopted children could receive a Testamentary bequest (not exceeding one-third) if the deceased made a will during his life; then, according to the will, a share can be given to him according to the Sharia method.
Adopted children can receive a gift. If the deceased did not make a will, then the heirs can gift (if they wish) something as a gift after the death of the deceased.
If you have situations where children are adopted, you can follow the above ruling, which was confirmed with Wassiyyah's Islamic ruling advisory team. However, you can consult any other knowledgeable scholar if your situation differs from what is described above.
Both legal and Shariah law are aligned in this respect in most countries. For example, New York and Shariah laws are similar as they both have laws preventing the adopted child from inheriting from two sources. Unlike New York law, where the adopted-out child loses inheritance rights from the birth parents, under Sharia law, the adopted-out child always keeps a right of inheritance from the birth parents but cannot inherit from adoptive parents. (REF- New York Domestic Relations Law - DOM § 117 (McKinney 2012). REF- The Guiding Helper: Main Text and Explanatory notes, Abu Qanit Al-Sharif Al-Hasani, 276 (2002)).