Maddie and Ben have been dating for nine years and they know each other inside and out. Maddie's younger sister, Mia, has been dating Casey for seven weeks. With a shared c'est la vie attitude, Mia and Casey announce they're getting married and having a baby. It's news that throws Maddie for a loop. Surprisingly, the girls' parents, who have recently adopted a carpe diem sort of philosophy, couldn't be more pleased.