Fiat also own Ferrari....how could you forget that

Actually Ferrari own Maserati and Fiat own Ferrari. So in that sense FIAT owns Maserati. But Ferrari are more or less in control of Maserati.

FOrd own various other brands like Ford, Jaguar, Aston MArtin.

BMW own BMW and Rolls Royce.

Volkswagen own Volkswagen, Audi, Skoda, Bentley.

Mercedes own Mercedes Benz, Chrysler, Smart, Maybach.

GM own many companies like Chevrolet, Pontiac, Jeep, Hummer, Daewoo, Subaru.

Toyota own Toyota and LExus

Honda own Honda

The Japanese companies do not expand much....they just manufacture cars and use mainly one or 2 brands.

Nissan own Renault and Peugeot.