Resolution criteria
This market resolves YES if any member of the Trump family receives the accolade, dubbing them a knight of the British Crown or any other sovereign authority by January 1st, 2040. An honorary knighthood without the accolade ceremony will not count. The Trump must be physically present to be dubbed.
Resolution will be verified through The London Gazette, which maintains a list of honorees going back to 1940, or official announcements from the Royal Household. Honour recipients are announced twice a year—at New Year and on the King's official birthday. Suggest official sources for other knighting authorities!
Background
Former Presidents Ronald Reagan, George H.W. Bush, and Dwight D. Eisenhower all became honorary knights of the United Kingdom; Eisenhower by the Order of Merit, Reagan and Bush by the Order of the Bath. Such honorary knighthoods are conferred by the King on the advice of the Foreign and Commonwealth Office, on those who have made an important contribution to relations between their country and Britain.
France, The Netherlands and Vatican City also dub knights with the accolade. Between question creation and close time, other countries may adopt or cease the practice.
Considerations
According to the U.S. Constitution,
"No Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State."
This constraint would require Congressional approval for Trump to formally accept a knighthood while holding federal office. However, a Trump may be knighted who does not hold office.