i'd really love to see the brother she's close in age to! i was thinking they started off highly competitive and antagonistic towards each other as children, but when they started training to take on the kingdom's wards it finally hit them that it wasn't about who was the best between them. it's about being the best they both can possibly be for their people and each other.
if you were thinking of going female, i'd love a sister she adores the crap out of and will never, ever escape being fussed over. basically i want a badass, super tight-knit royal fam.