Prince Harry and Meghan Markle’s decision to step back from senior royal duties in favor of civilian life in the States may have irreparably fractured their relationship with the British monarchy — but it had the opposite effect on the relationship between now-King Charles and his mother, Queen Elizabeth II. The current monarch, 75, and Britain’s longest-serving monarch — who died in September 2022 at the age of 96 — agreed that the polarizing couple had to either remain fully in the royal fold or jump ship, rather than participating in select public duties, as biographer Robert Hardman told P…