Cousin is a sewage hoarder

My cousin who is 17 collects poo and pee in jars and bottles... He keeps them under his bed. He also has a couple of paint buckets full of sewage on the balcony outside his room.

Weird thing is I'm 20 and used to collect pee also (not poo, though) around his age. I'm wondering if maybe this is a normal thing for teenage boys?