Board Thread:Questions and Answers/@comment-124.106.165.201-20130206083740/@comment-2151409-20130309113356

Ouka is 16: http://www.mangahere.com/manga/07_ghost/c080/11.html. She was three years old during the Raggs War.

Teito was four years old near the end of the Raggs War: http://www.mangahere.com/manga/07_ghost/c028/20.html. So Teito is only a few months older than her. :)