This story was updated on April 7 to include a comment from Justice Thomas.

Harlan Crow, the 74-year-old Dallas billionaire and real estate mogul, is close friends with Supreme Court Justice Clarence Thomas and gifts given as part of that friendship are now raising eyebrows about possible violations of financial disclosure laws.

Crow is chairman of the board of Dallas-based Crow Holdings, the private family office of the Trammell Crow family with more than $16 billion in assets under management that span more than 850 properties throughout the United States.

The nonprofit news organization ProPublica reported that Crow gave Thomas luxury trips that weren't disclosed by the conservative justice to the public in what appears to be a violation of a financial disclosure law. Crow, a mega donor for the Republican party, put Thomas up at his private resort and other exclusive retreats, flew the Supreme Court justice on his private jet and hosted Thomas on vacations in his 162-foot superyacht, among trips that span two decades, according to the ProPublica report based on dozens of interviews and documents.

Justices are required to publicly report any gifts valued at more than $415 or anything of value that isn't fully reimbursed, according to filing instructions for the judiciary. There are some exceptions to this general rule, including having dinner or staying at a friend’s house. However, transportation such as private jets and travel by superyacht are not exempt and should be disclosed, according to the judiciary disclosure instructions.

In an emailed statement sent to CoStar News through a representative for the Supreme Court, Thomas said he has been friends with Harlan and his wife Kathy Crow for more than 25 years, joining them on family trips in that time.

"Early in my tenure at the court, I sought guidance from my colleagues and others in the judiciary and was advised that this sort of personal hospitality from close personal friends, who did not have business before the court, was not reportable," Thomas said in the statement. "I have endeavored to follow that counsel throughout my tenure and have always sought to comply with the disclosure guidelines.”

The committee of the judicial conference responsible for financial disclosures revised its guidelines last month to specify that justices must report travel by private jet, as well as stays at commercial properties, such as hotels, resorts and hunting lodges. Thomas, who has served on the nation's highest court since 1991, said it is his “intent to follow this guidance in the future.”

In response to ProPublica's article Thursday, Crow emailed a written statement to CoStar News acknowledging the decades-long friendship he and his wife have shared with Justice Thomas and his wife Ginni.

"The hospitality we have extended to the Thomas’s over the years is no different from the hospitality we have extended to our many other dear friends," Crow said in the emailed statement. "We have been most fortunate to have a great life of many friends and financial success, and we have always placed a priority on spending time with our family and friends. Justice Thomas and Ginni never asked for any of this hospitality."

Harlan Crow is the third son of the late Margaret and Trammell Crow. His father, a former Navy man, returned to Dallas after serving in World War II and founded Trammell Crow Co. Under his leadership, the firm rose from developing warehouses to becoming one of the nation's preeminent development firms, creating some of the tallest skyscrapers in Dallas, including Trammell Crow Center and Chase Tower, and across the country.

The Texas State Historical Association says Trammell Crow pioneered the idea of "building on speculation" and using short lease arrangements to raise rents over time. His company also was known for forming partnerships to complete projects rather than bear all the risk alone.

The family eventually sold the Trammel Crow Co. in 2007 for $2.2 billion to what is now CBRE, the world's largest commercial property brokerage.

Harlan Crow joined his father in real estate in 1974 after earning a bachelor's degree from the University of Texas at Austin. He took the helm of Crow Holdings in 1988 to manage the family's fortune.

Part of that legacy was creating Old Parkland, an exclusive office campus in Dallas built on what was once a hospital. There, Harlan Crow turned his fascination with history into a work of real estate art. After buying the property in 2006, he reimagined what was once a plot of land surrounding the first brick hospital in Texas, built in 1913, into a modern campus that has become a sought-after office address for private family offices, high-net-worth individuals and wealth managers.

"The Crow name is synonymous with quality and thought of in the most utmost regard in terms of reputation," said one Dallas real estate executive, who spoke about Harlan Crow on the condition his name would not be used in a story about the ProPublica report.

Nods to Americana feature throughout an urban-style office campus that continues to expand to this day. The development includes more than 600,000 square feet of space throughout multiple buildings on a campus filled with stone sculptures, bronze statues and murals — many depicting historical figures — manicured gardens and reflecting pools.

That love of history has spilled over into Harlan Crow's personal home in Dallas that has a large collection of Americana. During a home tour a few years ago for a local newspaper, Harlan Crow offered a glimpse into his collection, including a 1493 pamphlet based on Christopher Columbus' hand-written letter to King Ferdinand and William Pierce's hand-written notes from the Constitutional Convention in 1787.

Harlan Crow's appreciation of history is apparent in at least one gift ProPublica said he gave Thomas that the justice disclosed: a $19,000 Bible that once belonged to Frederick Douglass.

Harlan Crow said in the statement that he and his wife have never asked about a pending or lower court case or discussed one with Justice Thomas during their friendship.

Harlan Crow said, "We have never sought to influence Justice Thomas on any legal or political issue," and he was unaware of any friends in their circle ever lobbying or seeking to influence the justice on any case, adding he "would never invite anyone who I believe had any intention of doing that."

On numerous occasions, Harlan Crow said he and his wife "made contributions to projects celebrating the life and legacy of Justice Thomas," as they have done with other leaders. None of this was at the request of the justice or his wife Ginni, he added.

"We did so because we believe Justice Thomas to be one of the greatest Americans of our time, and we believe it is important to make sure as many people as possible learn about him, remember him, and understand the ideals for which he stands," Crow said. "We will continue to support projects that advance this goal."

Through a spokesman on his behalf, Crow declined further comment to CoStar News outside of the emailed response Thursday.

Nancy Gertner, a retired federal judge appointed by President Bill Clinton, told ProPublica that it's "incomprehensible" that someone would accept those kinds of undisclosed gifts as a sitting judge. When she was on the bench, Gertner said, she was so cautious about appearances that she wouldn't mention her title when making dinner reservations.