Alma 3
I don’t think we consider this situation very often, but I am confident that there were regularly people of Nephite descent who were only loosely associated with the Nephite nation and who interacted casually with Lamanites who were similarly loosely affiliated and who subsequently intermarried. That would explain one of the reasons that the Lamanites despite losing so many people during wars, always had a massive population advantage. In fact, the Lamanites were most often not a unified people. They were, for most parts of history, a generalized collection of many different groups who did not follow the traditions of the Nephites, and who could be rallied in opposition to the Nephites by those who wished to rally them.