The plaintiffs include children of Sen. Robert F. Kennedy and Ethel Kennedy, and a son of Sen. Edward M. Kennedy, all of whom are buried at Arlington. Health and Human Services Secretary Robert F. Kennedy Jr. did not join his siblings in the suit against his own administration.

In a statement, Rory Kennedy and Maxwell Kennedy said the arch would "cast a shadow over our democratic principles" and undermine safeguards meant to protect the cemetery. "A towering arch casting shadows across the graves of our father, mother, and uncles, as well as the graves of so many who have served our country, would also cast a shadow over our democratic principles," they said.

The filing, submitted hours before Veterans' Day, seeks to join an existing federal lawsuit that combines challenges from Vietnam War veterans, an architectural historian, and the governments of D.C. and Virginia. The Arlington County Board has also filed a separate suit in Virginia.

The Kennedys argue that the arch would permanently degrade the experience of visiting the gravesites. "Plaintiffs would never again be able to appreciate both sites as they always have before, and as the Kennedy family always intended," they wrote in the 27-page complaint.

JFK's gravesite was intentionally placed on the same axis as the bridge connecting Arlington House to the Lincoln Memorial, with his personal secretary remarking that he was "the link between Lincoln and Lee." The eternal flame has burned since his funeral in November 1963. The family says they were assured that the design would safeguard visibility of the flame from the bridge.

A recent forensic analysis cited in the complaint found that the arch would cast shadows over tens of thousands of graves, darken JFK's memorial on 50 days of the year, and briefly block the eternal flame on nearly half of those days. The Kennedys said they often visit in the morning for privacy—exactly when shadows would be most pronounced.

The Trump administration has raced the arch through federal approvals, culminating in a final green light from the National Capital Planning Commission last Thursday. But within moments of the late-night approval, District Court Judge Tanya Chutkan issued an order blocking construction for two weeks while she evaluates the legal challenges.

One central argument against the arch is that it lacks congressional approval. The administration maintains the arch is justified by a century-old authorization of two never-built columns at the same location. Chutkan wrote last week that "merely to state this argument is to reveal its flaws."

The White House has characterized the arch as a tribute to military heritage. "It is unfortunate to see that some members of the Kennedy family have joined the litigation against the Arch as the project is intended to honor our heroes who rest in Arlington Cemetery," White House spokesperson Davis Ingle said. "We will continue making the case for this beautiful and fitting monument and are confident we will be fully vindicated as this litigation proceeds."

Max Kennedy told NPR that his family is acting to protect Arlington from "the arbitrary, capricious vanity of one man." He said the arch has bypassed standard rules and public input. "This arch is being constructed at the whim and whimsy of an autocrat," he said. "It's a vanity project, and it's completely different than the memorials that dot the city and that enrich the life of the city."

Georgetown University law professor David Super said the Kennedys' involvement strengthens the plaintiffs' standing. "I can imagine ... that a judge on any level would feel uncomfortable denigrating their concerns over their family graves the way the Supreme Court denigrated the plaintiffs' interest in the White House ballroom case," he wrote in an email. "And coming at a time when the Administration is hinting that it might tear down the Kennedy Center, this certainly makes the President look insensitive or even hostile to his revered predecessor."

Several Kennedy family members have spoken out against Trump's attempted takeover of the Kennedy Center, which is the subject of a separate lawsuit.

Arlington National Cemetery is the final resting place for more than 400,000 service members, veterans, and their relatives. Critics, including many veterans, say the arch would disrespect those buried there and disrupt funeral services. They also point to the administration's estimate that construction would involve 20-hour days, interfering with the 24 to 27 funerals held each weekday.

In a separate filing Tuesday, Ret. U.S. Army Brig. Gen. Steven Anderson warned that the arch would endanger national security, calling it a "high-payoff target" and citing risks from storing ammunition and launching drones near D.C.'s airport.

The future of the arch will likely be decided by the Supreme Court, experts say, though Democrats have vowed to use their forthcoming congressional majority to block construction and investigate potential wrongdoing.