Thael would actually be among the older ones. Magdalena is the oldest (3 February). Depending on how you look at it, she's either 21 already, or 22. Kat would be the youngest (6 December). Olivia has yet to turn either 21 or 22. I haven't given too much thought to which it is, as I guess it doesn't matter really—the characters are 21 or there about.