King Charles and Prince William are on the same page in one area when it comes to Prince Harry and Meghan Markle’s United Kingdom return. The father-son pair are “completely united on the Sussexes not representing the royal family,” author Russell Myers told People, in a cover story published Tuesday. The duo are reportedly “without a doubt … in sync” on the matter. Charles, 77, confirmed last week that his youngest son, who turned 42 on Tuesday, and daughter-in-law, 45, are not working royals but “private citizens.” In a statement — which Harry and Markle have reportedly taken issue with as they consider themselves “public figures” —…