Is the husband not obligated to spend on his wife and her children from a previous husband if he believes that by doing so, he is spending on her children?

The husband is not responsible for the upbringing and care of his wife's children, but his kindness towards them carries immense reward. He is obligated to provide for his wife's maintenance in a reasonable manner, including food, drink, clothing, housing, medical care, and the like, and he is not permitted to withhold it. If the children live with him and he does not voluntarily provide for their expenses, then the wife must pay from her own money the cost of their food, drink, clothing, and medical care, while the husband bears what the wife needs for herself. If the husband refuses to house the children with him and requests their contribution to the rent, he is entitled to that.