wa aleikum salam dear sister
Yes the Quran tells us alhamdullilah.
The brothers in law are non-mahrams so a woman should behave toward them as she should behave toward any other non-mahram. To cover in front of them, to not kiss and hug them, inchallah.
Surah An-Nour 31
"Tell female believers not to reveal their adornment except to their husbands or their fathers , or their husbands' fathers, or their sons or their husbands' sons, or their brothers or their brothers' sons, or their sisters' sons, or their (Muslim) women ( i.e. their sisters in Islam), or the female slaves whom their right hands possess or old male servants who lack vigour or small children who have no sense of feminime sex".
take care dear sister and welcome here.
:salam2: