this thread is getting astray so, better to stick the true side. what if father-in-law starts taking interest into ur marital matters such as why did you wake up so late? or sorry i can't mention but your father never uttered even a single word like this ever in ur life. one should do what with such MAHRAMS
Sorry to say in say nikah karna mana hai per maharam naheen ho jaatay.
Where in quran or hadith it says that father in law and mother in law are mahram.
You can hence prove that they are mahram because they can’t have nikah.
Nikah karna to kisi ki biwi say bhi kisi mard ka mana hai to is tarha koi ghair aurat kisi ghair mard kay liaay mahram naheen ho jati jub tuk wo kisi aur ki biwi na ho.