Reminds of the JW family who hosted the book study at their home...they finally had to put locks on their bedroom doors so much had gone missing (now why didn't they just refuse to have the book study there?)
I knew 2 women at work whose adult children who lived at home were taking money from her purse. She started keeping her money on her person in one of those travel wallets. Then she noticed that small radios, stereos, and TVs were missing. Did she ask her children to leave although there were the only possible suspects? No...better to replace the stolen items than lose her children's "love." They were using the money to buy drugs. Not that this is your case but it shows that this is more a theft of your trust than your money.
The other one set up a "nanny" cam and caught her son on tape stealing from her purse. How you deal with that is tricky. She gave him a month to find a place to live and changed all the locks afterwards.
Blondie (not so trusting any more)