Bristol Palin's pregnancy and engagement to Johnston became national news during Republican John McCain's 2008 presidential campaign. Sarah Palin was his running mate.
After McCain and Sarah Palin lost the election, Bristol Palin went on to write a book about being a single teen mom after she and Johnston broke up. She also appeared on the TV shows "Dancing with the Stars" and "The Secret Life of the American Teenager." Johnston posed for Playgirl magazine.
Johnston's representative told UsMagazine.com Tuesday Sunny Oglesby, Johnston's 20-year-old girlfriend, is pregnant. The couple have been dating for more than a year. Johnston and Bristol Palin are both 21.