Answer:
My eight-year-old brother is a pest. He has black hair, he' short for his age. He gets up early on Saturday mornings and wakes everyone up because the cartoons are on, on weekdays, we have to make him get up to get ready for school, he waits until the last minute to put his clothes on. When he doesn't get his way, he whines until he gets it. He's a spoiled brat, he always gets his way with our parents. This is the boy I have to put up with everyday.
Explanation:
You don't have to mention his age or his height more then once, and there are periods and commas where they're not supposed to be. and shorten the sentences the best you can because you won't keep someone hooked to what you've written, keep it short.