Although the gratitude that Lamoni’s brother feels is clear, his comment that Yahweh “has made these things known unto us beforehand” is puzzling. Before what? The only contextual clue is that Yahweh loves the parents as much as the children. What difference is there between parents and children, and why should we assume anything other than that Yahweh would love both?
I argue that “these things” mean, not gospel principles, but rather an awareness of the spiritual danger to the parents of taking up arms again. The children were not in the same danger since their participation in blood sacrifice would have been much less than that of their parents. “Beforehand,” I believe, refers to the Anti-Nephi-Lehies’ knowledge that an attack is coming in which the normal response would be to take up arms. Armed with this foreknowledge, they can make a principled and thoughtful decision about their response.