What indications are there that there is sibling rivalry in this community? The answer is in chapter 3 but I am having trouble finding it.
Jonah's feelings of resentment toward his annoying little sister is indicative of sibling rivalry.
Lily is her Daddy's little girl; Father affectionately calls her "Lily-billy", gently soothes the waters after Mother scolds her, and speaks tenderly to her, softly explaining Gabriel's feeding needs. Although Jonas doesn't outwardly compete his father's attention, growing up and realizing that he is different has him feeling insecure, and Lily's careless, childish prattle is really getting on his nerves. Jonas is resentful when Lily thoughtlessly points out that his eyes are different, and he scornfully imagines that Lily will be a Speaker when she grows up because she is never quiet. His annoyance with his sister leads him to picture her being publicly embarassed by the current Speaker because of her untidy hair ribbons, but that only reminds him of a time when he was a victim of such attention himself.