What is the ruling on a woman uncovering her face before her husband's foster father?

Uncovering the face before the foster father-in-law is not permissible according to Sheikh Al-Islam Ibn Taymiyyah, based on the saying of the Prophet, peace and blessings be upon him: "What is forbidden by lineage is forbidden by fosterage." The father-in-law is not forbidden to his son's wife by lineage, but by affinity. And based on the Almighty's saying: "and the wives of your sons who are from your own loins." The foster son is not among the sons from one's own loins. Therefore, the wife must observe hijab in front of her foster father-in-law. If she separates from his son, she is not permissible for him, as a precaution, given that this is the opinion of the majority of scholars.