smugness
Most intriguingly, the parents never told Ambrose and Justine that this kind of family unit wasn’t how most or even any other families had arranged themselves. So until the siblings went to school, they understood their family as the norm and, by that point, had so incorporated the idea of four parents into their concept of family that they seemed to feel an assured smugness at their abundance of parents compared with their schoolmates’ paltry one or two.