What is the ruling on the wife's family concealing their daughter's illness before marriage? Is the husband sinful, or is he obliged to pay the deferred dower if he divorces her due to her inability to have intercourse and the deterioration of her health after marriage?

Your marriage to this girl is valid, and you have no option to annul it. You are obligated to pay her the entire stipulated mahr (dowry) because you consummated the marriage with her after becoming aware of her illness, and because her illness is not among the diseases that necessitate an option [for annulment]. If the wife desires a divorce due to harm she is experiencing, there is no blame upon her for giving you money or waiving the deferred mahr (khul'). Her refusal to meet you and her continued residence at her family's home without excuse makes her a nashiz (recalcitrant wife), and thus her right to maintenance is forfeited. There is no sin in divorcing her, but it is advised to be patient with her, especially since she is pregnant, for Allah Almighty says: (But perhaps you hate a thing and Allah makes therein much good).