What is the ruling on marrying a second wife and concealing the matter from the first wife and the one about to be married, knowing that the first wife is ill and infertile, and the husband desires to have children?

A husband must be truthful with his wife if he intends to marry another. He is not legally obligated to inform her, but informing her might be better. However, it is not permissible for him to lie by claiming to have divorced a woman he never actually married. If the wife consents, the decision is hers; otherwise, he should look for someone else. Understanding between co-wives is rare, and what usually prevails is jealousy and rivalry. This is why scholars have forbidden two wives from living in the same dwelling without their consent.