AMSTERDAM.- Rembrandt’s 1661 double portrait “Two African Men” is a rare depiction of free Black men in 17th-century Amsterdam and a particularly prized work in the collection of the Mauritshuis, a jewel-box museum of Golden Age masterpieces in The Hague, Netherlands.

Art historian Abraham Bredius, the museum’s former director, bequeathed the painting to the Mauritshuis upon his death in 1946, along with two dozen other paintings by Rembrandt and other painters.

But Bredius’ heirs are demanding the return of all 25 of those paintings, saying that the Mauritshuis has not complied with a condition of the bequest, which stipulates that all of the artworks must always be on permanent display. Only a fraction are on view.

On Thursday, lawyers for the heirs filed a motion in The Hague’s district court, calling the museum’s behavior a “gross violation” of the terms of the bequest. They are demanding an annulment and the immediate release of the artworks to their family.

“Bredius was very clear what he wanted,” Otto Kronig, one of the claimants, said in an interview. “It’s a slap in the face of Abraham Bredius. If he had known this, he wouldn’t have done that bequest.”

René Timmermans, a Mauritshuis spokesman, said in an email that the museum could not comment “as long as the case is being researched (and this might take a long time.)” In the past, the Mauritshuis has expressed doubts about the authenticity of some of Bredius’ donations, and the museum’s director said one of the Rembrandt portraits was too “ugly” to hang in the galleries.

The case is being brought by Otto and Sophia Kronig, the grandnephew and grandniece of Joseph Kronig, an art critic and close friend to Bredius who was named as the historian’s sole heir. Kronig was about 30 years younger than Bredius, who often referred to him as “a protege,” and sometimes as “a stepson.” Several art historians have suggested that Kronig was Bredius’ romantic partner, but his grandnephew said there was no evidence of that.

Otto Kronig said that when he and his sister visited the museum to see the works in 2021, they were shocked when they couldn’t find most of them.

They saw four Rembrandts from the Bredius trove in the galleries, including “Saul and David” and “Homer,” both key attractions for the museum. But many of the other paintings, including works by less famous 17th- and 18th-century painters like Jan van Goyen, Salomon van Ruysdael and Jean-Baptiste-Siméon Chardin were nowhere to be found. The museum’s online catalog listed 20 of the 25 as “not on view.”

Bredius was “very strict in his bequest,” said Gert-Jan van den Bergh, the Kronigs’ lawyer. “What we see now is that the museum accepted the collection, but not the conditions.”

Bredius, born in 1855, was known as a colorful and combative expert on the Dutch old masters. He wrote several controversial articles questioning the authenticity of paintings attributed to Rembrandt and Johannes Vermeer, and made his own attributions. He became the director of the Mauritshuis in 1889, and retained the post for 20 years.

During his tenure, he was responsible for the acquisition of more than 120 major artworks, including one of the museum’s star attractions, Carel Fabritius’ “The Goldfinch,” which he found at a sale in Paris in 1896, and which later inspired the Donna Tartt novel. He also welcomed Vermeer’s “Girl With a Pearl Earring” into the museum, a bequest from a Hague collector.

At the same time, Bredius was building his own private collection, which decorated his mansion in The Hague’s historic center. He was a savvy buyer who scoured the corners of the market. His New York Times obituary noted that he once bought a Vermeer for $100 and sold it 30 years later for $100,000.

According to several art historians, Bredius was as openly gay as a man could be in the Netherlands at the turn of the 20th century, and his sexual orientation was the subject of innuendo in Dutch newspapers. He met Joseph Kronig some time around 1905, through art world connections in The Hague.

Kronig, born in 1887, was also an art historian and served for one year as the director of the Frans Hals Museum in Haarlem, but left to work independently as a critic, art dealer and collector. Bredius, who was independently wealthy, “enabled him to do so,” wrote historian Wessel Krul; in 1920, he bought a villa in Florence for Kronig, according to Bredius’ biographer Louise Barnouw-de Ranitz.

“For the sake of form, Kronig was always referred to as Bredius’ ‘stepson,’ and otherwise their relationship not alluded to in conversation,” Krul wrote. But its real nature was “an open secret,” he added.

Otto Kronig, who has read many of the documents from his granduncle’s personal archive, said, “I haven’t seen anything that indicates something other than a professional relationship,” adding: “It was a work relationship, but a close one.”

Bredius and Kronig traveled together in search of artworks to Germany, France, Spain, Italy and Russia, according to the Barnouw-de Ranitz biography. On a trip to the United States, they visited American industrialist Henry Clay Frick, who was forming an art collection that he would later bequeath to the City of New York as the Frick Collection.

This may have inspired Bredius to do something similar. When he moved from The Hague to Monte Carlo, Monaco, in 1922, he sold his house to the municipality and left behind his art collection, porcelain, silver and furniture, on the condition that the city open the house to visitors. On his death, he donated these works to The Hague, establishing the Museum Bredius.

Many of the best artworks went to the Mauritshuis in a separate bequest. According to court papers, Bredius was frustrated that some artworks he had earlier donated to the Rijksmuseum in Amsterdam had been “hung in a staircase in the dark.” With his Mauritshuis bequest, he stipulated that “except in case of restoration or in case of fire,” the works “shall always remain present” in the museum.

The museum has been explicit about its reasons for not showing some of them. Two of the paintings that Bredius donated as Rembrandts — “Study of an Old Woman” and “Tronie of an Old Man” — are now listed on the museum’s website as “after” Rembrandt and of “uncertain” attribution. Neither of those works are on display.

In 2019, the Mauritshuis’ director, Edwin Buijsen, told the Dutch newspaper Trouw that he didn’t believe that “Praying Woman,” donated by Bredius as a Rembrandt, was genuine either. “It’s a very ugly painting,” he was quoted as saying. “It has been hanging in the depot for 30 years.”

In 2007, the Mauritshuis took “Saul & David,” off the wall to examine it and settle doubts about its authenticity that had been swirling for decades. Bredius bought it in 1898 and described it as one of Rembrandt’s triumphs, but the attribution was questioned in the 1960s by Horst Gerson, a Rembrandt scholar of a new generation. By 2015, the Mauritshuis had confirmed the attribution and put the work back on display.

There are usually arguments on both sides in attribution disputes, but Bredius did make one ostentatious error.

Late in life, while he was living in Monaco, a stranger brought Bredius a biblical scene, “The Supper at Emmaus,” which appeared to be a 17th-century oil painting. The historian pronounced it an undiscovered Vermeer and a missing link in the artist’s oeuvre. He also encouraged the Museum Boijmans Van Beuningen in Rotterdam to purchase the work, even donating some of his own money to help buy it. The museum unveiled the painting to great fanfare, giving it pride of place in its galleries. “We have here a — I am inclined to say the — masterpiece of Johannes Vermeer,” Bredius said at the time.

Forty years later, however, the true identity of the work’s painter became known: a 20th-century forger named Han Van Meegeren. The revelation tarnished the art historian’s reputation, despite arising long after his death.

When Bredius died in 1946, Kronig stayed on in the Monaco home until his own death in 1984. Having no children of his own, he named his nephew, Otto Joseph Gregorius Kronig — the grandfather of the claimants in the lawsuit — as his successor.

Asked what they would do with the paintings if they got them back, Otto and Sophia Kronig had different answers.

“It’s not a good time to talk about that,” Otto said. “It’s in the distant future now, so we don’t want to go there yet.”

But Sophia Kronig wanted to make her position clear. “We’re not planning to sell them,” she said. “It’s not about the money. It’s important to us they get attention, and that they’re not in some backroom where no one can see them.”

This article originally appeared in The New York Times.