Every wizard/witch has a soulmate. When you find your soulmate you stop aging or de-age so if you are 11 and your soulmate is 30 he/she will de-age and you will continue to grow until you reach the age they became and you will remain like that if/until your soulmate dies. Harmony Granger is Hermione Granger's twin sister and she just so happens to be the soulmate of James Fleamont Potter.
6 parts