A good start! You should also look into getting your own bank account, fully separate from your family.

Also you're mom never questioned where your lazy ass bro got a fat wad of cash? Something about the story doesn't add up.

Finally if you want to be really petty, just wait until their next bday or Christmas comes around. Don't get them anything and if they ask, tell them to stop being greedy since they already stole a $150 gift.