Over the past few days, the German luxury automaker Porsche has moved into high gear with the launch of its latest model, the Panamera, a 4-door, 4-seater sedan that it hopes will reverse flagging sales and maintain its status as the world’s most profitable auto maker. But even as the motoring press descends on Stuttgart to test drive the new car, the Panamera launch is being overshadowed by a bizarre feud in the company’s founding family that is starting to damage both Porsche and its sister company, VW. It’s a nasty, vindictive battle that, in keeping with bad cases of sibling rivalry, risks spiraling out of control and hurting everyone involved, including the shareholders, customers and workers at the two German automakers.