The billionaire Reuben brothers of Britain - best known as property tycoons that are worth a collective $12.6 billion - have found themselves in smack dab in the middle of the art world's biggest controversy.

One of the biggest question marks in the industry is the true owner of Guzzini Properties, Ltd., which is an investor claiming ownership of a work sold by Inigo Philbrick, an art dealer who has mysteriously vanished after being sued repeatedly for various types of alleged fraud involved art he allegedly owned and helped broker sales of.

An attorney in New York who represents Guzzini, Wendy Lindstom, confirmed that David and Simon Reuben are its owners, according to Bloomberg.

Guzzini has filed a lawsuit over the work, Rudolf Stingel’s 2012 untitled portrait of Pablo Picasso, as of October. The complaint stated that Guzzini had bought the painting from Philbrick in 2017, along with two other pieces, for $6 million. Guzzini reportedly cosigned the work to Christie's for its May auction, where it fetched $6.5 million.

Except there was one problem: two other firms apparently had stakes in the painting prior to Guzzini.

Satfinance Investment Ltd. bought a 50% share in the work for $3.35 million from Philbrick in January 2016 and German art investment firm FAP GmbH says that it agreed in February 2016 to buy the Stingel from Philbrick in its entirety for $7.1 million. Guzzini is now seeking a legal declaration that it is the sole owner of the work and is seeking its return.

Lindstrom said: “My clients are philanthropic collectors, who, unfortunately, must now litigate to secure their rightful title to artworks after their good-faith, arm’s-length purchases.”

Until now, it had been a mystery as to who was behind Guzzini - and Christie's, the auction house holding the work, is waiting for the courts to decide who the rightful owner is.

A spokesperson for the auction house said: “Given the ongoing nature of the multiple legal cases in this matter, Christie’s agrees that determination of rightful ownership of the Stingel work by the courts is the next necessary step forward.”

The Reubens have been lenders to landmarks like New York's Plaza Hotel and the Grosvenor House hotel in London. Last week they committed to helping finance Dreamscape Co.'s acquisition of the Rio All-Suite Hotel from Caesars.

Recall, days ago, we wrote about the disappearance of Philbrick amidst allegations of double dealing and inflating the prices of art he was purchasing with business partners.