I loaned my brother $1000 years ago, after he borrowed and repaid a $2500 loan. It took well over five years to get the money back. He said, "Since you stopped asking about it, I figured I must have paid you and forgot." Um...no. He also borrowed money from our 78yo limited-income widowed mother, as did my sister.
When we all received some money from an inheritance, all debts were paid between parties. Finally.
And, no, I would not lend my siblings money. I've rather soured on family. I wish my siblings well, but after all the crap I put up with growing up and continuing to this day, I wouldn't miss them if I never saw or heard from them again. They don't want to be a part of my life (unless there's something in it for them, of course)? Fine by me.