The following is a conversation that just took place in our playroom, where my 8-year-old son D- and 5-year-old daughter M- were each playing with Legos in their own way, after my buddingly verbal almost-2-year-old son E- happily waltzed in. I think it pretty well captures their relationship most of the time, these days.
E- (idly content): Wehhh-gooooooes...
M- (sounding not unlike Ian McKellan's Gandalf): E-, this is my tower, and you cannot touch it!
E- (decisively oblivious): TOUUUUCH!
M-: No, DON'T touch it!
You may enjoy my previous D- conversations, M- conversations, and (wife) J- conversations, as well as my future E- conversations.