Reference: I’laam al-Mu’aasireen bi-Fataawa Ibn ‘Uthaymeen – Page 182
Question: A man married a woman; Is it permissible for his wife to then unveil herself in the presence of her husband’s step-father?
Response: It is not permissible for the wife to unveil her face in the presence of her husband’s step-father; this is because he is not the [blood] father of her husband, and therefore is not her mahram.
