If he decides to press charges on only me, what would happen?

Sister signed some of my brother’s checks, sent me into a store to buy groceries and such with the checks. They have my license number on them because they had to ask since I bought cigarettes. I didn't even look at the check. I thought it was my dad’s but I was wrong. They're were like 3 checks written, with the total adding up to no more than $500.