My Wife's Sisters Unveil Themselves to Me When I am Driving Them in My Car

Question :

I would like to inform you that I married a girl who has three sisters who are younger than she, and I live with my wife's father in order to help him in his affairs, but the problem is that on many occasions, we mix in the house when eating. And my wife's sisters join us, and they have their heads covered and their faces unveiled. And sometimes, I drive one of them to school, or to college or the library. What is the ruling of the Islamic Law on this?

Answer:

There is no sin for you in living with your wife's father due to the aforementioned reason, which is to help him in his affairs, or for any other permissible reason. But your wife's sisters must veil themselves from you and cover their faces because the face is the greatest beauty and He, Most Glorified says in Surah An-Nur.
"and not to reveal their adornment except to their husbands, or their fathers, or their husband's fathers.

And it is not permissible to be alone with any of them or to go with one of them to the school, or the library alone with her. according to the words of the Prophet:
"A man Mahram may not be secluded with a woman except with a Mahram."

And his words:
"A man should not be alone with a woman, for verily Satan makes a third "

So if you want to take one of them to school, then there must be a third person with you so you are not alone, and through his. presence you will be safe from Satan's incitement to evil-may Allah protect us from his evil whisperings.

Source:
Ibn Baz
Fatawa Islamiyah, Vol. 5 Pages 133-134