The ages don't line up perfectly, Ryosei is actually a few years younger than Tadashi but hey in the future some people look younger than they are, lol. Miki is older than Rumiho though.... but she looks pretty young so we'll just chalk it up to classic Dawson's Casting.
Let me preface this by saying I'm not very good at getting the STO character creator to look like real people, that aside I don't think I've seen anyone mention her yet but one of my inspirations for Ril'el was Natalie Dormer. I remember being struck with her when I first saw her in The Tudors.
It's mostly the attitude she can convey, particularly in her eyes. I find them very, very captivating and when I write Ril'el I always want it to be her eyes that creates a connection with those she interacts with.
For a portrayal of Seral, I 'interviewed' more than 70 possible actresses, based on general size/shape and face to get that far. The closest I found that I thought would be able to pull of the voice was narrowed to two.