My answer was mixed. Under ideal conditions, with one child strapped to a two story roof 6 miles away, and the other, chained to the chimney on top of another 2-story house it would be possible to achieve 6 miles. 20 miles? no. Many of you have seen these in stores and on Amazon, that are similar to the ones in the picture, any most of them you find with any long range claims will be FRS/GMRS radios. FRS, were usually under $20 radios that the kids could have fun with, and 14 channels to choose from.
To get a GMRS license is easy - no test required. All you need is to fill out the license form, be 18 years of age or older, and enclose a check for $85 (good for 5 years).
That's a fairly important part to leave out, especially after you've bought them and been using them for awhile. Because these handhelds operate in UHF (Ultra High Frequency), they are more line-of-sight in communications. Your conditions, and distance my vary. The fact a license is required does not.