Is the mother's husband a mahram to her stepdaughters?

The questioner : A man married a woman who had children, and he fathered daughters with her. Is the mother's husband a mahram to their daughters?

The Shaykh : Yes, he is a mahram to them. The rule, may Allah reward you, is that when a man marries a woman and has intercourse with her, all of her descendants fall under His saying: The rule is: "When a man marries a woman and has intercourse with her, her ancestors and her descendants, however far down the line, become forbidden to him" whether they are daughters, sons, or granddaughters. Adhere to this rule. Likewise, her ancestors, meaning her mother and her grandmothers, whether on the mother's side or the father's side, are also forbidden to him. Similarly, if a woman marries a man, his sons, his grandsons, his granddaughters, and his grandfathers, whether on the mother's side or the father's side, as well as his father, are all mahrams to her. We have four branches: the husband's ancestors, the husband's descendants, the wife's ancestors, and what? The wife's descendants. These branches establish the prohibition merely by the contract. How is the prohibition established? The wife's ancestors and descendants become forbidden to the husband, and the husband's ancestors and descendants become forbidden to the wife. However, for the wife's descendants, it is required that he has had intercourse with her, meaning he has consummated the marriage. Take this rule so that you may be at ease, because some people may err in it, even among students of knowledge. But this is the rule. And when "ancestors and descendants" is mentioned in this context, meaning in the prohibition of marriage, it includes ancestors on the father's side and ancestors on the mother's side, and descendants in the form of sons and descendants in the form of daughters. Yes, do you understand now?

The questioner : O Shaykh, what if he divorces her?

The Shaykh : Even if he divorces her or dies before her.