While not officially Yamaha Faster Sons, the Coolest Brothers XSR700's by Oberdan Bezzi play the same game.
Initially the brothers were a pair. While similarities exist, they take their inspiration from different places. One apes Euro retro machines and the other American roadsters. The Euro brother features a bash plate, the American a chin spoiler and Factory Yamaha Racing paint.
Obiboi also went on to add two new brothers. The CroXity which is a cross between a motocross bike and a commuter and dressed up like Yamaha's factory motocross bikes from the 70's.
The last concept is an endurance racer. which draws from endurance racings heyday in the 80's. Big twin bug eye headlamps, half fairing, short tail and clip ons.
Obiboi operates in a purely conceptual realm, which is unfortunate because 1 or 4 of these could very well find a fine home with us...