Young marriage

My boyfriends best friend has never liked one of my boyfriends girlfriends before me. So now that he likes me he keeps asking my boyfriend if he's going to marry me. And then his best friends family was taking bets on when they think he and I will get married. They say he'll be the fast approaching 20 when we get married but I'll 19 and I know young marriages have a lower chance of lasting. Opinions? Any women who were married young have stories?