Representative George Santos, a Republican facing scrutiny over a web of false claims, including a family connection to the Sept. 11 terrorist attacks, will bring a former firefighter who did rescue work at ground zero as his guest to the State of the Union on Tuesday.

Mr. Santos’s guest, Michael Weinstock, a Democrat who once ran for the House district that Mr. Santos now represents, said that Mr. Santos officially extended an invitation two weeks ago. Mr. Santos confirmed the invitation in a speech on the House floor on Monday.

Mr. Weinstock said he had decided to attend because he is currently suffering from a neurological condition related to his time as an emergency worker and wanted to raise awareness of the needs of those like him.

“I’m cautiously optimistic that I’ll be able to stay focused enough on the issue of 9/11 responders receiving the health care that they need without being sullied by George Santos,” Mr. Weinstock said.

To do so has already proven challenging. Mr. Weinstock, a lawyer, said that he was let go by his law firm last week over his decision to attend the State of the Union with Mr. Santos.

Members of Congress generally get one ticket to bring a guest to the State of the Union address, and many of them make symbolic choices either to highlight issues or make political statements.

But Mr. Santos’s choice of Mr. Weinstock is particularly curious given the questions over the congressman’s purported ties to the Sept. 11 attacks. He has said that his mother, Fatima Devolder, was at the World Trade Center that day, at times claiming that she was working as a financial executive there. In a Twitter post from July 2021, he said that “9/11 claimed my mother’s life.”

Mr. Santos’s campaign website currently says that Ms. Devolder “survived the tragic events on September 11th, but she passed away a few years later when she lost her battle to cancer.”

Ms. Devolder died in 2016, according to her obituary and local news coverage. On immigration documents reviewed by The New York Times, she told government officials in 2003 that she left the United States in 1999 and had not returned since. Mr. Santos’s friends and former roommates could not recall Ms. Devolder ever having worked in finance, and in immigration documents, she described herself as a housekeeper and home aide.

Mr. Santos’s assertions about his mother was one of many that have come under scrutiny after The Times disclosed that he had misled voters about his background and raised questions about both his personal and campaign finances. Mr. Santos has since been largely ostracized by politicians on both sides of the aisle. Ten fellow Republican representatives have called for his resignation, while others have said they refused to associate with him.

Like Mr. Santos, Mr. Weinstock has faced some scrutiny about his own ties to Sept. 11. When he was running in the Democratic primary in 2020 against former Representative Tom Suozzi, the president of his former fire company said that there was no record of Mr. Weinstock being at ground zero on behalf of the company. But other former firefighters said they worked with Mr. Weinstock on rescue and recovery efforts there, and Mr. Weinstock has provided to news outlets at least one photo of him from that day.

Mr. Weinstock would not comment on the doubts around Mr. Santos’s claimed links to Sept. 11, saying he had been avoiding news coverage about it in part because of his illness and in part because of his personal ties to the congressman.

According to Mr. Weinstock, he and Mr. Santos first became acquainted in April 2021 when they exchanged Instagram messages about comments that Mr. Santos, who had already begun his second campaign for Congress, was making on the trail.

They reconnected in the summer of 2021, after Mr. Weinstock suffered a foot injury that later led to complex regional pain syndrome, a chronic nerve disorder in which patients develop persistent pain to an injured area on the body. The injury left Mr. Weinstock unable to walk for a time, and Mr. Santos visited his home to check on him.

That September, on the 20th anniversary of the Sept. 11 attacks, Mr. Santos posted a photo of Mr. Weinstock on his Instagram account. “I can’t thank Michael enough for his brave actions and for having been a first responder,” the caption read. “Michael also happens to be a Democrat and former congressional candidate in 2020 who believes in serving his country.”

Mr. Weinstock, a volunteer firefighter from 1990 to 2001, said that his illness was tied to pollutants he inhaled during rescue efforts at the rubble of the World Trade Center. At least two medical studies have found a link between nerve-related conditions like Mr. Weinstock’s and Sept. 11 rescue workers. But the World Trade Center Health Program, which provides health care to ground zero responders and Sept. 11 survivors, does not offer medical coverage for those conditions.

In the immediate period after his injury, Mr. Weinstock said, he was unable to work because of his condition. A year and a half later, he says he still experiences severe pain nearly every day that can make it difficult to focus, and he sometimes uses a cane to walk.

During his 2022 campaign, Mr. Santos offered to “host a GoFundMe” to raise money for Mr. Weinstock’s medical care, Mr. Weinstock said, noting that he declined the gesture, fearing the fund-raiser would be used as part of Mr. Santos’s political campaign.

But Mr. Weinstock said that Mr. Santos returned to him in December, saying that he wanted to sponsor a bill that would push to get Mr. Weinstock’s condition covered by the health fund. Mr. Santos asked Mr. Weinstock to write a briefing paper that would help support the cause. But the issue was dropped after The Times’s initial report on Mr. Santos and others that followed.

Mr. Weinstock said that he did not vote for Mr. Santos last year but was touched by Mr. Santos’s concern over his condition, and he was eager to bring more awareness to the issue. Still, he said that he found the congressman’s falsehoods on the campaign trail to be “inexcusable” — a sentiment apparently shared by his former law firm and its leader, Wesley Mullen.

According to Mr. Weinstock, Mr. Mullen told him, “I know your motivations are pure, but George Santos is so toxic, I don’t want any association with Santos and this firm.”

Mr. Mullen declined to comment.