What is the age of حضانة (custody) for a boy, and does the father have the right to reclaim him after he reaches the age of حضانة, especially if the father is married and the mother is not? And does the father have the right to reclaim the boy upon the marriage of the mother, who is 30 years old?

The jurists differed on the time when custody ends, and the most preponderant opinion is that it is at the age of seven. When it ends, the child is given the choice between their parents. If the child does not choose one of them, lots are cast between them, unless there is an impediment to custody for one of them. If the custodial mother marries, her right to custody is forfeited, and the father has the right to take the child, unless there is someone with a stronger claim to custody or she relinquishes it to the father.