Does the death of the wife fall under the "separation" stipulated in the books of custody, and is the maternal aunt entitled to the custody of her deceased sister's children if the father is present, taking into consideration the noble Hadith, "The maternal aunt is in the position of the mother"?

The mother has the primary right to custody before the age of discernment, unless she remarries or has an impediment. If the mother dies, remarries, or is unfit for custody, the primary right to custody then goes to her mothers (maternal grandmothers). If they are absent, the right of custody transfers to the paternal grandmothers according to the majority of scholars. However, the Hanbalis, in a well-known narration, hold that it transfers to the father, provided there is a woman with him for custody.

As for the order of priority between the maternal aunt and the father in custody, the Hanafis, Hanbalis, and one of the two opinions of the Shafi'is prioritize the father. In contrast, the Malikis and the other opinion of the Shafi'is prioritize the maternal aunt. If the maternal aunt is married to a man who is not a mahram to the child, she has no right to custody. Some scholars have used the story of Hamza's daughter and the Prophet's (peace be upon him) saying: "The maternal aunt is in the position of the mother," as evidence for prioritizing the maternal aunt over the father in custody. Since this issue is a matter of disagreement among jurists, it is best to refer to the Sharia court to decide the matter.