Need help with Internet

Here's the situation. We have 5 computers at home, mine which is connected through cable and works fine, and 4 others that are laptops. Now, when I download something, or someone else does, the internet for everyone else gets all fucked up and you can't even browse the web. Is there an option that exists in routers, that could identify how many connections it has, and somehow split an even speed to each computer. So, say we have 30mb/s, and 5 computers, so 6mb/s for each computer, and if I download, others won't get affected by it.