Seven of Health and Human Services Secretary Robert F. Kennedy Jr.'s siblings, plus his nephew and cousin, are suing President Trump, the Interior Department and National Park Service among others to stop Trump's planned "Triumphal Arch," citing its unavoidable blocking of light over their family's graves at Arlington National Cemetery, which are "sacred spaces."

"Our parents, Robert and Ethel Kennedy, and our uncles, President John F. Kennedy and Senator Edward M. Kennedy, are laid to rest at Arlington National Cemetery. Our uncle Joseph P. Kennedy Jr., who lost his life serving our country in World War II, is also memorialized there," RFK Jr.'s siblings Rory Kennedy and Maxwell Kennedy said on behalf of the family in a statement released by their lawyers at Democracy Defenders Fund.

"We believe Donald Trump has violated the laws and procedures established by Congress to protect this most sacred national memorial," they said, portraying the arch as an attack on democracy itself.

"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, undermining the safeguards established by our elected representatives to protect this hallowed ground for generations to come," they said.

The fund makes clear the family sees Trump's plan as a personal affront.

"The arch would block views of the Kennedy Gravesites and Eternal Flame from Arlington Memorial Bridge — a sightline specially chosen by the Kennedy family," it says. "The arch would also cast a shadow over the Kennedys’ graves, especially in the early morning when the family traditionally visits."

White House spokesperson Davis Ingle told ABC News the family's motion to intervene was "unfortunate," as the arch's purpose is "to honor our heroes who rest in Arlington Cemetery."

Though the "activist" U.S. District Judge Tanya Chutkan temporarily blocked the start of construction for at least two weeks in response to Virginia and D.C. legal action, the Trump administration is "confident we will be fully vindicated as this litigation proceeds," Ingle said.