When I download an app on the Ipad the same app starts downloading on the Iphone 5?

Is that suppose to happen? Does that mean I don't have to pay for Minecraft Pe twice if I want them on the two devices?

Your iPad is downloading the same app because of iCloud. It won't charge you any extra costs, but every time you take a photograph or download an app; it will share the photograph or app to any other device that is registered on your iCloud.

iCloud is a sharing facility which only Apple users can have. It supports iPods, iPads, iPhones and iMacs.

It will not charge you twice for this feature, your iPhone is simply set up to automatically download any new content you purchase through iTunes or the app store. However, if you wish to turn it off for whatever reason you can find solutions on this page.

http://support.apple.com/.../kb/ht4539