People close to Ms. Barry say she is decidedly not the mixed-up one in the family.

Although she did not start law school until after her son was in sixth grade, Ms. Barry has had a four-decade career as a prosecutor and federal judge, achieving a measure of celebrity independent of her brother. (“This is not the Trump Princess,” The Chicago Sun-Times wrote in 1989.) Some friends say they did not even know she was part of the famous family.

“There was a story in Time magazine or something, and a couple of the other lawyers come in and go, ‘Did you know Maryanne is a Trump?’ ” said Donald J. Volkert Jr., a former New Jersey Superior Court judge who became a close friend of Ms. Barry’s. “And I said, ‘What’s a trump?’ ”

Ms. Barry earned a reputation as a tough judge with a strong command of her courtroom. In 1989, as a district court judge in Essex County, N.J., she blocked a plea deal that would have freed two county detectives accused of protecting a drug dealer. She forced the case to trial, where the detectives were convicted and received 12- and 15-year jail terms. She presided over the conviction of Louis (Bobby) Manna, the Genovese crime family boss accused of trying to assassinate a rival, John Gotti. And in 1996, she chastised federal prosecutors for trying to deport a former deputy attorney general of Mexico, calling their efforts politically motivated, unconstitutional and “Kafkaesque.”

As an appellate judge for the Third Circuit — with chambers in Newark and jurisdiction over Delaware, New Jersey, Pennsylvania and the United States Virgin Islands — she has forcefully rebuked prosecutors and defense lawyers, but also trial judges she considered inept. And in 2000, still new to the appeals court, she wrote a 40-page unanimous decision calling a New Jersey law banning late-term abortions “unconstitutionally and incurably vague” and saying that it put an “undue burden” on women’s constitutionally protected right to the procedure.

Ms. Barry, who is tall and has a similar, if more abundant, coiffure of blond hair to her brother’s, has made it clear that she never felt in competition with him. She has also said that is a good thing.

“I knew better, even as a child, than to even attempt to compete with Donald,” she told New York magazine for a “power siblings” edition in 2002. “I wouldn’t have been able to win.”