Brothers from the father are not mahram to sisters from the mother

Question: My father has a wife other than my mother, and that woman has children from my father. We also have a maternal aunt—she is my mother’s sister—who breastfed me and my brothers from my mother. She has sons and daughters.
The question is: Is it permissible for my brothers from my father to sit and talk with my maternal aunt’s daughters without hijab? Given that my brothers from my father were not breastfed by my maternal aunt, who is my mother’s sister, do my maternal aunt’s sons and daughters become our brothers and sisters?

Answer: It is not permissible for your brothers who were not breastfed by your maternal aunt to consider themselves mahram to your maternal aunt’s daughters, because they were not breastfed by her. Rather, the mahram of your maternal aunt’s daughters are those who were breastfed by her completely—meaning five breastfeedings or more, while they were within the first two years—based on the saying of the Prophet (peace and blessings be upon him): , and what is established from Aisha (may Allah be pleased with her), who said: “It was among what was revealed in the Qur’an that ten known breastfeedings make a person mahram, then they were abrogated by five known breastfeedings. The Prophet (peace and blessings be upon him) passed away while the matter remained as such.” Imam Muslim recorded this in his Sahih, and al-Tirmidhi in his Jami', and this is his wording. Also, based on the saying of the Prophet (peace and blessings be upon him): , agreed upon by al-Bukhari and Muslim.