I remember when my brother was a kid. I didn't always have time, he annoyed me every chance he got, he wanted to be tucked into w/e I was doing. As a kid myself I didn't understand this. I was annoyed by this. I didn't know any better. I guess part of me was jealous.
Today I regret not spending more time w/my brother, not trying to teach him by influence, not spending more time just hanging out, reading books, w/e kids do. I was busy trying to climb trees, spend time with kids my age, getting into trouble etc. We are two worlds apart now and I really regret it.
Spend as much time with your little brother as you can. Lead him by example. He might do silly little things that seem idiotic to you, only because you know better. Teach him that these are not the right things to do. Do so without screaming or making a big thing of it. If anything make a joke of it, ask him if he had a good time swimming with the fishes, but humans can't breathe underwater...or something goofy. You'd be amazed at that little moment you took out of your day to ackowledge his actions, right or wrong, will do. It will bring you closer, you will slowly become someone he looks up to...listens to. That bond should be important, he is your family he should be someone you care about, at least enough to try and enlighten him.
There might come a day where you don't have that annoying brother around throwing a fit and asking you to watch and he shoves his head into the toilet and flushes the bowl. And I am sure that would suck, even if it doesn't seem so at this moment in time.