I saw something about this in another forum on here. Marriage. Some people are for it, some are against it.

We can have the best of both worlds. For the people who want marriage, the big hand of god/dess could drag and drop a couple inside the ruins, then instead of going inside, they would have a littler ceremony, and then never be allowed to breed with anyone else. This would also open up some intersting behaviours for the villagers such as nagging, checking honeydo lists, couples that relax together instead of alone, they could have fights that stop them from working, or work together for higher productivity, etc. And the children could follow them around the island. When one partner dies the other could suffer a loss of health, or refuse to work for a year.

If you wanted to make it more traditional, the builders could build a church, and the other villagers could be invited to the wedding.

For people who don't want marriage, you just don't do the drag and drop.