Whilst it's really sad you paid money for this, if you read the description of the App carefully it does exactly what it say it will do. It is a joke app. You tell your friend that the app can locate them anywhere in the world, PROVIDED THEY ARE STANDING RIGHT NEXT TO YOU. When you run it, low and behold, it will show you that they are in the same location as you.
The reason it does not work for your bothers phone is because he is not standing right next to you. If he was, it would work! Just like it would find me if I was standing right next to you. It never does anything other than report that the other person is next to you.
The many many one star ratings for the app should have indicated to you that maybe it was now what you thought it might be!