As Salaamu Alaikum,
Is it permissible for a daughter in law to drink from the same water / cup as a father in law?
Wa Alaikum As Salaam,
Yes, it is permissible to do so since the daughter in law is a mahram to the father in law on account of marriage.
And Allah knows best
Mufti Waseem Khan
This answer was collected from DarulUloomTT.net, which is operated under the supervision of Mufti Waseem Khan from Darul Uloom Trinidad and Tobago.