No. You cannot claim the expenses for having your sister-in-law live there. If you claim your wife's parents as your dependents and actually pay MONEY to your SIL for their care so you could work then you could enter it as a dependent care credit. But you cannot enter her "room and board."
It sounds like you have a tough family situation that all of you are just trying to make the best of.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
