What should a husband do who discovered after marriage that his wife has been ill since birth and is mentally incapacitated, with her family being aware of this and concealing her illness, and she is now pregnant? Should he divorce her and take the children?

The majority of scholars hold that the defects which validate the right to annul a marriage, and which must be disclosed to the suitor, are those that impede conjugal relations, or are repulsive or contagious diseases. Some scholars, however, are of the view that any defect that causes aversion in either spouse necessitates annulment. If your wife had insanity or a similar condition, her family was obligated to inform you of her defect, and you would have had the right to annul the marriage after becoming aware of the defect. However, since you accepted and continued to live with your wife after becoming aware of her defect, your right to annulment has been forfeited according to the majority of scholars. You are permitted to divorce her if there is a need due to her bad character and difficult companionship. If you divorce her and you have young children from her, the general rule is that custody belongs to her, unless there is an impediment such as insanity, and the Sharia judge is the one who decides on this matter.