What are the motifs in The Hero and the Crown by Robin McKinley?

Family relationships is a reocurring idea in the story. First there is the relationship between Aerin and her cousins. Galanna is jealous of Aerin, jealous because she is the daughter of the king and receives many breaks for this reason. Galanna is also jealous because Tor, the young first sola, is clearly in love with her. Galanna wants to be queen. Galanna's best chance to become queen is to marry Tor, but he has eyes for no one but Aerin.