How to download an app without getting it on my other apple devices?

All the apps and music I get automatically gets downloaded onto my mom and brothers iPhone. How can I stop that?

I think you, your brother and your mom is sharing the same account in iTunes. I suggest create a account for each family on iTunes, so that they won't get the same apps. You may also visit this page for best and latest apps for iPhone: http://www.appfavour.com/ios/iphone