Is it permissible for a man to marry a divorced woman who has children from a previous marriage and wishes to keep her children with him, and would he be sinful if he did so, given that the children’s father refuses their living with the mother’s husband?

There is no objection to a man marrying a divorced woman who has children and keeps them. However, he is not permitted to assist her in preventing their father from his right to raise or have custody of them, as Allah Almighty says: "And do not cooperate in sin and aggression." The new husband bears no sin if his wife takes her children out, provided he does not conspire with her to deceive their father into keeping custody of them and traveling with them without his permission.