12 year old Stealing

Me and my mother have had enough of my brother stealing from us. He done this twise now, Granted what he has stolen is nothing big, just food, food out of the fridge, a box of Malteser's, And now my Easter egg (not a small one either a large one the Malteser egg with 4 bunnies) But we dont want to get to the stage where we can not trust him.
He does have underlining problems, he has ADHD, However we have brought him up well, He knows the difference from right and wrong, our farther is a prison officer so he knows the consequences of stealing, he is a very kind boy, happy, content, And we know he is not hungry, for he has 3 meals a day with snacks.
it hurts for all day i was talking about how i was going to eat it, how we where going to go to the shop, buy him another so he can eat one with me, and knowing hed ate it, knowing that i was going to eat it, didn't tell me or my mother.
We just dont know what to do. we dont want to feel like where being to harsh but i have had experiences with friends *Tara (name has been changed) she started stealing small, a chocolate bar from the fridge, Sweets of her brothers and sisters, but eventually it lead to her stealing money.
Where just so worried and disappointed, we dont know what to do, We dont want it to get to the stage where he steals bigger things. e.g. money

Thank you for your time and consideration to read are message and reply.

Faithfuly SilverMoonShine

[margypops]

See I dont consider its stealing if an older child /teen/adult is hungry and goes to the fridge for food, do you do it ? why do you consider that stealing ..why keep chocolate in the fridge if they are not allowed to have any ..In my opinion you are sounding harsh , does your mom feel the same way , He has challenges he could use your kindness and understanding ..

[RockRose]

Your family dynamic sounds very unusual,  silver.

You speak like you and the mom are the parents of this 12 year old sibling of yours.  

I agree with Margy,  when people get food out of the fridge that's called "snacking" and not "stealing",  although it sounds like in the case of this chocolate thing (you had one,  he didn't have one) he was jealous and took it and ate it.

Did he have any Easter candy of his own at all?

I think you're making more of this maybe than is there,  and I think also it's not healthy to align yourself with your parents as if you are a parent to this boy.