Around 500 million watched in 1973 as Queen Elizabeth's only daughter, Princess Anne, married Lieutenant Mark Phillips. (Random fact: Anne's first boyfriend was Andrew Parker Bowles, who would become Camilla's ex-husband. Anne couldn't marry him, because he was Catholic.)
Mark went on to have an affair, fathering a child in 1985 with a New Zealand woman. In 1989, Anne and Mark separated, and they divorced in 1992. Later that year, Anne became the first royal divorcée to remarry since Henry VIII, as she married Commodore Timothy Laurence in front of 30 guests.
Perhaps hoping they'd have more-normal lives, Anne's two children, Peter and Zara Phillips, do not carry titles, the first grandchildren of a reigning monarch to not do so in over 500 years.