Is it permissible to live in one house that brings together the children and the children of the divorced wife, taking into consideration their ages and genders? And is it obligatory for the wife's daughters to wear the hijab in the presence of the wife's son?

The fundamental principle is that your daughters should not live with your new wife's son in the same dwelling due to the absence of a Mahram relationship between them, and the potential for temptation and corruption that could result from their cohabitation. However, it is permissible for them to live together in one house out of necessity, provided that the rulings and etiquette of Islamic law are observed. This includes avoiding private seclusion (khalwa) and suspicious mixing, and ensuring that they do not appear before him without a hijab.