I hate it when my brother uses my hair products

My brother and I share a bathroom. (It's horrible). I used to keep my shampoo and conditioner in the shower. I don't anymore because he would always use it. That may sound just plain greedy and selfish of me. But hear me out. My hair is dyed and really dry. I wash it twice a week. My brother washes his hair everyday. I do not buy cheap shampoo. I don't buy expensive salon stuff either, but my shampoo and conditioner aren't any cheap generic brand. He would end up using the majority of my shampoo and conditioner. And then when it was empty, he'd just leave it in the shower. So when it was time to wash my hair, the bottle would be empty and I'd have nothing. It irritated me so much! So now I keep my hair products in my room. Away from him.