For more than two decades the heirs of a world-renowned Jewish collector have been petitioning the Hungarian government to return more than $100 million worth of art, most of which has been hanging in Hungarian museums, where it was left for safekeeping during World War II or placed after being stolen by the Nazis and later returned to Hungary.The requests have been rebuffed, as have appeals to the government from current and former United States senators, including the Democrats Christopher J. Dodd, Hillary Rodham Clinton and Edward M. Kennedy. Finally, in 2008, a Hungarian court ruled that the government was not required to return the art. Now, in what experts say is the world’s largest unresolved Holocaust art claim, the heirs of the Hungarian banker Baron Mor Lipot Herzog have filed a lawsuit in United States District Court in Washington demanding the return of the art collection they say is rightfully theirs. The lawsuit has been filed against Hungary and several museums that it oversees.The suit, filed on Tuesday, includes an unprecedented twist: in addition to the more than 40 artworks explicitly identified in the filing – including paintings, sculptures and other works by masters like El Greco, Lucas Cranach the Elder, Zurbarán, van Dyck, Velázquez and Monet – lawyers are also asking the Hungarian government for an accounting of all art from the Herzog family in its possession.”It’s a very emotional subject,” David de Csepel, a great-grandson of Baron Herzog who lives in Los Angeles, said of the collection’s fate in a telephone interview. Mr. de Csepel, who said he was speaking on behalf of about a dozen relatives, explained that this lawsuit had come after decades of frustration with the Hungarian government. “I want to see justice done. My great-grandfather was one of the most famous collectors in all of Europe. His passion and love of art is well known.”