Ever since the FBI seized a Renoir supposedly purchased at a flea market by a Loudoun County driving teacher, the chief legal adversary of the woman known as “Renoir Girl” has been the Baltimore Museum of Art.

But now, as the battle for the tiny landscape heads to a federal trial in January, Renoir Girl has a new foe: her brother.

This month in sworn depositions for the federal case, Matt Fuqua, a Northern Virginia property manager, said he raised questions about the claim by his sister, Martha Fuqua, that she bought the Renoir for $7 at a West Virginia flea market in late 2009. The painting was reported stolen from the BMA more than six decades ago.

Matt, 50, said he told the lawyers deposing him, “My mother told Martha to ‘return the painting to its rightful owner — the museum — so all of this goes away.’ ”

Martha, 51, declined to comment for this article, saying only, “Call my brother.”

The sibling warfare has gone far beyond the murky provenance of “On the Shore of the Seine,” painted by Renoir in 1879. Martha was charged by Fairfax police last month with breaking into the apartment of her brother’s girlfriend. And Matt became the target of a lawsuit filed by his sister this month in Fairfax County court in an effort to evict him and his girlfriend from their mother’s property.

At a hearing last week in U.S. District Court in Alexandria to set a trial date, Martha Fuqua’s attorney for the Renoir case, T. Wayne Biggs, declined to be interviewed.

The acrimony between the Fuquas comes just two months after their mother, Marcia Fouquet, died at age 85 after a bout with cancer. Fouquet was a painter who attended art college in Baltimore at the time of the Renoir’s reported theft from the BMA in 1951 and who, according to some witnesses, kept the Renoir in her Fairfax home since the 1980s or 1990s.

“My mother wanted us to get along more than anything in the world,” Matt said. “This whole Renoir thing has made my sister and I — who used to be kind of close — now be enemies and at war.”

“I told [my sister] to give the painting back, and that ‘You’re going to get in a lot of trouble,’ ” he said. “She said, ‘You don’t know what you’re talking about.’ ”

In his Nov. 14 deposition, Matt contradicted his sister’s timeline that she had bought the Renoir in late 2009 and stored it at her Loudoun home until mid-2012. Matt said he testified that the Renoir couldn’t have been only at his sister’s Loudoun home during those 21 / 2 years. His girlfriend Jamie Lynne Romantic, a Northern Virginia real estate agent, discovered the Renoir while cleaning out his mother’s Fairfax studio in late 2011, he said.

In an interview, Romantic, who so far has not been deposed, detailed how she found the Renoir in 2011 as she was sorting through boxes in Fouquet’s art studio in Great Falls.

“I came across this little painting,” she recalled. “It was pretty. The actual frame was pretty. It said ‘Renoir’ on it. I placed it on a couch.”

When Fouquet walked upstairs to check on Romantic’s progress, the mother saw the Renoir on the couch, Romantic said.

“What were you going to do with this?’” she remembered the mother asking. “I said, ‘Just bringing it to you.’ She said, ‘This is priceless. It’s a real Renoir.’ ”

“Ms. Fouquet was an artist,” Romantic said. “I didn’t think to ask her, ‘Where did you get a Renoir from?’ ”

Hours later, Romantic recalled, Martha showed up at the house.

“Martha says, ‘If you find anything else like that painting, you need to call me immediately. That painting is worth $1 million,’ ” Romantic recounted. “Then she said, ‘My mom is giving me the Renoir to hold for safekeeping.’ ”

Nearly a year later, in September 2012, Martha tried selling the Renoir through an Alexandria auction house, which estimated that the 134-year-old painting would fetch as much as $100,000. In the auction’s run-up, Martha gave interviews to reporters about what was dubbed the flea-market Renoir but refused to reveal her identity, calling herself “Renoir Girl.”

But days before the bidding began, the BMA found internal records showing that the impressionist landscape, painted on a 51 / 2-by-9-inch napkin, had been stolen while on exhibit in 1951. The revelation prompted the FBI to seize the piece and set the stage for a federal judge to determine who gets to keep it: Renoir Girl or the BMA.

Earlier this year, Martha unmasked herself in her effort to get the painting back. She pleaded in court papers that she deserves the painting because she is an “innocent owner,” as defined by federal law. She had no clue when she bought the Renoir in a box of junk, she said, that it might have been stolen and subject to seizure.

Once Martha’s identity was revealed, The Washington Post called her only sibling, Matt, who initially said his mother had had the painting for decades, but then retracted his comments after conferring with his sister.

Several months later, their mother died, and the sibling relationship nose-dived.

On Oct. 10, Martha was arrested on a burglary charge by Fairfax police and jailed for five days for allegedly breaking into Romantic’s apartment on Fouquet’s Great Falls property and allegedly stealing Romantic’s jewelry, antiques and furniture, according to court documents. She was also charged with misdemeanor assault and battery for allegedly attacking her brother — a charge later dropped by prosecutors.

A hearing on Martha’s burglary charge is scheduled for December. Lucy Caldwell, a Fairfax police spokeswoman, said it’s against the department’s policy to allow media interviews with detectives on active cases.

Michael Harrington, Martha Fuqua’s attorney handling the burglary charge, denied that she broke into and entered Romantic’s apartment. He declined to explain where Martha was at the time of the alleged incident, arguing that the purported episode’s date is uncertain. But he said Martha is the trustee of her mother’s estate, and “she has the right to care for that property.”

In reaction to the burglary charge, both Matt Fuqua and his girlfriend sought and received temporary protective orders from a Fairfax General District Court magistrate, but judges later denied them lengthier orders. In his petition to the court in October, Matt wrote that his relationship with his sister has been decimated. “She said, ‘I’m dead to her,’ ” he wrote.

This month, Martha filed two lawsuits in Fairfax General District Court seeking to evict her brother and Romantic from their rented room and apartment on the mother’s property, and to recoup a total of $30,000 in what she alleges was unpaid rent.

Matt declined to comment on the lawsuits, other than saying he and his girlfriend spent several months tending to his ailing mother and maintaining her property.

“When I go to [services] at McLean Bible Church every Sunday, I am at peace, but when I leave church, I am pretty much stressed out about all this,” said Matt, who aspires to transform the property into a bed-and-breakfast and museum to showcase his mother’s paintings.

One mystery — not about his sister, but his mother — nags at him. Did Fouquet know how the Renoir was spirited out of the BMA in November 1951?

Before she died in September, Matt and his girlfriend pressed his mother on the Renoir’s origins. But she didn’t respond to their inquiry.

“She went catatonic,” Matt said.