1. If a brother in law drinks from a utensil, can his sister in law drink after him or does his wife have to drink first or vice versa?
2. Can a brother in law sit on the same bedding that his sister in law uses to sleep?
1. The sister-in-law should avoid drinking, whether straight or after his wife.
2. If there are doubts or feelings of lust it should be avoided.
And Allah Ta’ala (الله تعالى) knows best.