The Laqit does not inherit from the one who found it
Q: In 1370 A.H.,
my father saved a child whom he found wrapped in a cloth and sheltered by rocks at the top of a mountain in the desert. My mother looked after him and breastfed him without her having a child of her own at that time.
However, during the two years of breastfeeding, she became pregnant. This child whom my father called Ma`tuq was raised and brought up with us. At the present time, he is an army sergeant and my parents have passed away. My father has bequeathed that this person should inherit along with us. He is on good terms with the whole family. Is he allowed to inherit from our father with us? Is he considered a Mahram (unmarriageable relative) (Part No. 16; Page No. 10) for my mother and her daughters, taking into consideration that Ma`tuq was raised with us until he became adult and got a job? I hope that Your Eminence advises us on the inheritance and his relation with us. May Allah protect you.
your father and mother are to be thanked for what they did; taking care of this Laqit (foundling) until he grew up.
the breastfeeding that makes the child a Mahram means giving five or more feedings in the child's first two years. If your mother breastfed this child in this manner, he becomes her milk son, and he becomes a milk brother to her children. Allah (Exalted be He) says,
Forbidden to you (for marriage) are: your mothers, your daughters
to His saying
...your foster milk suckling sisters
Allah (Exalted be He) also says,
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
It has been authentically reported that the Prophet (peace be upon him) said, (Part No. 16; Page No. 11)
Wet-nursing makes unlawful what consanguinity makes unlawful.
It has been proven that
`Aishah (may Allah be pleased with her) said,
It was revealed in the Qur'an that ten known times of breastfeeding prohibit marriage then it was abrogated (and substituted) by five known times of breastfeeding, and the Prophet (peace be upon him) died while it was likewise.
It should be noted that what is considered to be one time of breastfeeding is when the infant takes hold of the breast and sucks milk from it; if he lets go, then comes back and sucks more milk, this is considered a second time of breastfeeding, and so on.
it is not permissible for the mentioned child to take your father’s name as if he is one of his sons. (Part No. 16; Page No. 12)
the child you mentioned cannot inherit your father, because he is not one of his heirs.
if it is proven that your father determined in his will to leave one-third or less of his property to this person, there is nothing wrong with that; you may also keep in touch with him and treat him kindly, for Allah (Exalted be He) will never cause the reward of those who do good to be lost. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.