What Did It For You?
I think it may be time for your 9 year old to talk to a counselor. If you think about it, if you live in a home with so many other people, it IS possible to miss out on certain foods, so he may have a valid point! Especially if he developed this observation at a young age. So it makes sense to stock up on 7 snack cakes before somebody else gets to them first. And from what you tell me about your family history, not being allowed to be hungry may have already been instilled into his way of thinking.
Maybe you could have a set snack time for everyone so he'll know he'll get something to eat. If he eats outside of the determined time, then he may have a problem. If it's fine with him to know when he is going to eat, then you can control that.
Maybe you could try replacing processed snack cakes with fruit or anything natural like cheese sticks or natural peanut butter. Processed carbs make you crave more processed carbs. Just a thought,
Mary