what is the fastest family car exsist

Never mind the Vauxhall Zafira VXR, the mad boffins at Mercedes have jemmied their 6.2-litre naturally aspirated V8 into the six-seater R-class, creating the world’s fastest production MPV. With standard four-wheel drive, the R63 catapults from 0 to 62mph in 5.0sec on its way to an electronically limited 155mph. Power is a massive 503bhp and torque an equally outrageous 465lb ft, all channelled through a seven-speed auto ’box. You’ve got to hand it to AMG– rather than expensively restyling the not exactly gorgeous R-class they’ve simply made it so quick that no-one will get a chance to glimpse it as it rockets past. That said, the limited styling touches such as revised bumpers and 20in wheels make the R63 easily the least ugly R-class. Inside, you get the same spacious six-seat cabin, meaning more of your friends can share in the rumbling sounds from the four exhaust pipes. The R63 goes on sale in the UK in October, priced from £74,115. Expensive, yes, but you might think it’s worth it to arrive before the children have even asked if you’re there yet.

There are so many variables that go into this it's not even funny. (but cool) if we're talking 4 door sedan, stock, I think it'd be the BMW M5, I could be wrong, but I can't think of any others at the moment.Oh, wait, I lied. The Cadillac CTS-V is faster than an M5 now. 556HP =P And for like SUV, (again, just off the top of my head, don't quote me here) I think the Cayenne Turbo is the quickest. but it depends what conditions. Wet or snowy, the Audi RS series. but I don't know many cars out of the US like vauxhauls etc.

how about a bmw or a benze with a v12?

Porsche Panamera Turbo is the fastest family sedan right now. The next fastest is the S65 AMG, followed by the CTS-V, followed by the the M5, S63 and S600 mercedes.