Well, the best thing to do is keep reading. This will help you understand what you are reading, if you read more. Don't try reading too fast; take it slower, and at a pace where you will be able to understand the material. Does it take you a long time to read? I know it is an old cliché, but practice makes perfect. The best way to improve reading comprehension is to keep reading. Also, you may one to try and quiz yourself, help you retain information.
Yes, there are other kids that do not need to do homework or study, but this is other kids. If it doesn't apply to you, don't try it. Find what way best works for you, and stick to it. Different people learn differently and and different paces, so you'll just have to find what works best for you.
You have potential for being smart, you are not dumb. Try not to compare yourself to others, I know it is hard, but everyone is smart in their own way and in their own right.
There really isn't any family genetics to being smart; however, this doesn't mean you are dumb because the rest of your family is smart. It just takes discipline and a plan of attack.
I know I've reiterated finding a way that works for you, but this is the key to success. Ways that work for others may not work for you. Good luck!