re: Your 9 year old son steals money out of your wallet

I always keep 20s, 100s are too hard to break anywhere.

Both need to be disciplined. Child number one for stealing, and child number two for snitching instead of convincing his brother to do the right thing and put the money back.

Two life lessons in one grounding.

Before you do that, start lifting things they like from their room when they are not there. See how long it takes for them to realize their shite is missing. Then hit them with the life lesson and grounding.