Wolfgang Porsche and his cousin Ferdinand Piech, both grandsons of founder Ferdinand Porsche, are facing a lawsuit from seven hedge funds over the carmaker's failed takeover attempt of Volkswagen.
Investors including US hedge fund Elliott Associates are seeking €1.8bn ($2.4bn, £1.5bn) in damages from the family business.
The company and its management are accused of misleading the market in the attempt to acquire the control of Volkswagen. Porsche had initially dismissed speculation that it was looking to acquire Volkswagen, but later admitted that it was controlling almost 74% of the company shares directly or indirectly.
Some investors were betting against Volkswagen shares, hoping for a decline in them in the absence of a takeover attempt from Porsche. The late disclosure by Porsche of an increased holding in Volkswagen resulted in higher share prices and losses for those investors.
Porsche, which has faced similar lawsuits in connection with the takeover, denied any wrongdoing, adding that the new legal action is "a trial tactic" and "without merit". The company said the new claim against the board members does not include any new content.
"Porsche SE and its supervisory board members will defend themselves with all available legal means," the carmaker said in a statement.
A previous lawsuit from the hedge funds, demanding $1.4bn, was thrown out by a New York court in 2012.
Nevertheless, Porsche's former CFO Holger Härter was found guilty of credit fraud during the takeover saga. Härter along with former CEO Wendelin Wiedeking was charged with market manipulation in Germany.
Porsche failed in its attempt to take over Volkswagen, as it fell short of buying the required 75% stake.
The company had largely been depending on borrowings for the acquisition, and the global financial crisis and the slump in the automotive sector made it difficult for Porsche to buy the remaining stake.
Already troubled by debts, the company was sued by a number of investors for misleading them.
In 2009, Volkswagen agreed to take over Porsche's sports car business in a surprise to the market and a dramatic turnaround of events.
Volkswagen acquired a 49.9% stake in the business initially in 2009. In 2012, the company acquired the remaining 50.1% stake to complete the takeover.