WASHINGTON — The Kennedy family, one of America's most famous political dynasties, has joined a court case aimed at blocking the construction of a triumphal arch in Washington, saying it would obstruct views and cast shadows over their relatives' gravesites. Nine members of the family filed a motion on Tuesday in federal court in Washington, DC, to stop the arch from being built, arguing that it obstructs views of the family’s gravesites in Arlington National Cemetery as well as “the memorials of hundreds of thousands of fallen American heroes.”The 250-foot (76-meter) arch, shown in a rendering to include a flame held by a 60-foot gold winged female figure and flanked by gold flying eagles, would be situated across the Potomac River from the Lincoln Memorial on a highway roundabout near the entrance to the Arlington National Cemetery.“President Donald J. Trump is attempting to unlawfully erect a massive arch that will permanently cast shadows over and damage historically significant sightlines to the existing gravesites and memorials established in the Kennedy family’s honor at Arlington National Cemetery, as well as to the memorials of hundreds of thousands of fallen American heroes,” the family wrote in the filing. The Kennedys argue the design and location of the massive arch would obstruct the clear sightline of the family’s gravesites, including the John F. Kennedy Eternal Flame from the vantage point of the Arlington Memorial Bridge, ultimately “destroying an essential element” of the gravesite’s design. The family says the Trump administration has “raced forward to build” the arch, which is “more than double the size of the Lincoln Memorial and the equivalent of a 25-story office building.”“Its location in Memorial Circle would situate the monument on an axis between the Lincoln Memorial and Arlington National Cemetery, obstructing a line of sight that was designed to represent the unification of the Nation following the Civil War and that has existed for nearly a century,” the family argues. The Kennedys are joining a lawsuit filed last month by Washington, DC, and Virginia. Veterans and preservationists, as well as Arlington County, have also sued to block the project. Opponents say the enormous scale of the arch and the location would also disrupt the sightline of the row of national landmarks that includes the Lincoln Memorial, Arlington House and the Robert E. Lee Memorial, and that the towering monument will break the solemnity of funerals of Arlington National Cemetery. The plaintiffs in the new filing include the children and grandchildren of President John F. Kennedy’s brothers – Sens. Robert F. Kennedy and Edward M. Kennedy – who are among the six family members buried at Arlington National Cemetery. The family is arguing they have particularly good standing to challenge the arch, because courts in the past have recognized families’ interests in protecting their relatives’ gravesites.“The gigantic proposed arch is an illegal interference with Arlington National Cemetery and the heroes remembered there, including at the gravesites and memorials of the Kennedy brothers and Ethel Kennedy. Only Congress has the constitutional power to authorize an intrusion of this magnitude,” said Norman Eisen and Steve Jonas of Democracy Defenders Fund, who are representing the Kennedy family members.“Today, members of the Kennedy family are joining with the other litigants in this case to protect this historic site–and to defend the rule of law and separation of powers.”A federal judge last week blocked construction of the arch for 14 days after a final vote approving the structure passed late Thursday despite fierce opposition from citizens who voiced concern during a marathon public hearing.US District Judge Tanya Chutkan, an Obama appointee who is overseeing one of the high-profile lawsuits to stop construction, ruled that the Trump administration would be prohibited from “initiating, making or otherwise effectuating” any “construction-related activity” near the proposed site of the arch. President Donald Trump has previously said he intends to complete the arch before he leaves office in two years, but the aggressive timeline has been complicated by the ongoing legal challenges. In a review released by the National Park Service in August, the administration acknowledged that the arch would have “adverse” effects on as many as 42 historic sites. The arch is just one example of the president’s efforts to reshape the nation’s capital to his own liking. Construction and renovation projects around Washington, from the Lincoln Memorial Reflecting Pool to the Kennedy Center, have figured heavily in his second term — something his critics have labeled “vanity projects.”The Trump administration contends Congress approved the arch more than 100 years ago when it also authorized construction of a bridge across the Potomac River. It has said that the arch would honor veterans. Numerous Democrats in Congress have vowed to block construction once they take control in January, after winning November's midterm elections.