News/ Duck Dynasty Star John Luke Robertson, 19, Is Engaged to Mary Kate McEacharn—See The Photo! by Corinne Heller Sun., Oct. 12, 2014 10:13 AM PDT John Luke Robertson, Mary Kate McEacharn Instagram Cue the Duck Commander calls of celebration! Duck Dynasty star John Luke Robertson, the grandson of family patriarch Phil Robertson, is engaged to girlfriend Mary Kate McEacharn. He proposed at a party on Saturday—while he and his family celebrated his 19th birthday! "I am so excited to marry my best friend," John Luke said in a statement to E! News on Sunday. "I know my parents married young as well, and they have always been examples of what 'could be' to me. Fast-forward 22 years and they are more in love than ever, and I hope Mary Kate and I are the same way in the years to come. God has truly blessed us." McEacharn posted on her Instagram page late on Saturday a photo showing her flashing a sparkling engagement ring and her new fiancé holding a sign that reads, "Future Mrs. Robertson." "Happy Birthday to the boy I'm going to marry," she wrote.