Yeah If the 3 huts your talking about is the love shack and the long house and the original (allready started) hut. then your at your max population and you have to get that builder on, you cant force the next living huts, they will start it when their ready, but make sure the builder is set to building. im not sure if they will start the hut if their not on building, ive never noticed cause ive always got the builder on that skill. so just be patient they will start it when they are ready for more villagers.