FaceTime call from Mac to iPhone 4S over 3G doesn't connect
I have the same problem. I assume that your brother's iPhone is on iOS 6 (which officially comes with the cellular FaceTime feature) and uses AT&amp;T (which blocks this feature). I've heard someone say AT&amp;T might start letting all iPhones use cellular FaceTime, but I believe the official word is that cellular FaceTime only works with AT&amp;T if you have a Mobile Share plan or if you have an iPhone 5. Meanwhile you'll have to call him with Skype or Google Hangout, or he'll have to go to WiFi.