The following clip from “Family Guy” demonstrates why you simply shouldn’t put yourself in a position to owe money to family members. It also demonstrates why you shouldn’t lend money to family, either. Although in the clip, the money exchange is due to a bet, this really goes for lending money as well.
Warning: Gratuitous, and hilarious, violence, as well as some language.
Both parties end up feeling guilty at the end – Brian for ducking out on the money he owed, and Stewie for causing Brian so much pain while trying to get the money. Also, everybody gets hurt. Even though your brother-in-law might not actually come after you with a flame thrower if you owe him money, he might feel like he wants to.
Simply put, don’t do it. It just causes problems.