How could I have never connected Nick's possibly having to leave with Rowan's leaving a year or two year earlier?
Well, I confess I never noticed it myself until I was writing that post!

But I am very close to my (two) sisters, so although we're not close in that TV 'we share everything' way (no sitting on our beds and talking about boys), I can make a reasonable guess at how they'll react in various situations, hence I wasn’t surprised by this in the books.