I need to know why my penis is small but when I wake up in the morning I am horny and my pants are down. It is just me and my brother in the room because we share one room, but I don't know if it is him or is it possible I jack off in my sleep.
Most likely you are having wet dreams. A wet dream is when you masturbate in your sleep. It is perfectly normal and happens because the glands which produce semen are full. Your body instinctively releases the pressure by masturbation while you are sleeping.