In celebration of the Fourth of July, John Green takes a close look at the First Ladies in our history for this week’s mental_floss video. Can someone be a First lady without being married to the resident? There have been cases in which the president’s daughter, sister, or niece took over those duties if the president had no wife. All of these ladies were pretty busy, either playing hostess, promoting their own causes, or trying to survive the spotlight of the White House.