Answer
(Fatwa: 582/577=D)
If there is separation (talaq, khula) between husband and wife owing to some reason and they have any child, then in case of son the mother has right to nourish it for seven years. Mother can keep him with her until he is able to fulfil his daily necessities. If the child is a girl the mother has right to nourish her till she is grown up. However, father will bear all the expenses incurred. In the above condition, if your wife wants to keep the children with her she can keep them till the age mentioned above.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband