What are the legal procedures for recovering the deceased brother's daughters, whose mother lives in Syria, especially after her engagement to a man who will take them to the United States, given the family's rejection of this and their desire to raise them with an Islamic upbringing in Saudi Arabia?

If the mother of the child being fostered remarries, her right to custody is forfeited and transfers to her mother (the child's grandmother). This is the view of the majority of scholars, based on the Prophet's (peace be upon him) saying: "You have more right to him as long as you do not remarry." The mother is not permitted to take the two daughters to a Western country, even if she has not remarried, due to the risk of exposing them to corruption and temptation. If she does so, her custody is forfeited, because one of the conditions for custody is residence in the child's country.