My sister in-law breast fed her adopted son more than five times at the age of 13 months. Is he considered Mahram to me as the boy's aunt i.e. can I remove my Hijaab in front of him? Please provide relevant Daleel.

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. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If your brother's wife has suckled the adopted child the milk that arises from the intercourse of your brother then the child becomes unmarriageable for you as we mentioned in Fatwa 86750: "The age at which an infant stops breastfeeding is two complete years.  Allaah Says (which means): {The mothers shall give suck to their children for two whole years, (that is) for those (parents) who desire to complete the term of suckling …}[Quran 2:233].

If after the two complete years another suckling woman gives suck to an infant, the latter does not become automatically a Mahram for her, and she is not considered a suckling mother for him; this is what is agreed upon by the Muslim scholars.  It is also the opinion of Abu Haneefah, Maalik, Shaafi'ee and Ahmad and their successors." Furthermore the Fatwa also reads: 'The number of suckling times by which a person becomes a Mahram is 5 times as in the Hadeeth of 'Aa'ishah who said: (What was first revealed from the Quran was that suckling 10 times, makes the person Mahram to his suckling mother.  But this was abrogated to 5 times (only).  The Prophet passed away, and it (the number of suckling) was still what is recited from the Quran).  She meant that the abrogation of the verse that reads “the number of suckling is 5 times” was abrogated so late that the Prophet died and some people were still reading that abrogated verse." (End of Fatwa quotation)

As for the extension of suckling relations to the relatives of the fostering parents, we said in Fatwa 90488: "It is written in 'Az-Zaad' a book of Hanbali school: 'Whenever a woman suckles a child he becomes her child as far as the rulings of marriage, looking at her, and being alone with her, are concerned. This child also becomes a child for the man, and the unmarriageable relatives of the foster-parents also become unmarriageable for the foster-child. This ruling applies to the foster-child only; it does not cover even his original parents and children'."

As for the Islamic ruling on adoptions, please refer to Fatwa 84422.

Allaah Knows best.