IIRC, which should help when doing the epilogue and endings, whoever ends up doing them - they follow recruitment/support order. Can you confirm this?
So it pretty much goes...
Characters recruited in Main Chapters (Lucina is between Henry and Say'ri, if I remember, and support list when chapters give two characters)
Characters recruited in Sidequests by Paralogue order (Donny, Anna, then the children starting with Owain)
Spotpass characters
And in the paired endings, the basic structure of each support is based on the males and Avatar, so they take priority order in the list. Like, Lissa will come up pretty early if she's unmarried, but could come in as late as Henry.
I'll need to double check this to make sure - once I'm done my work. Probably sometime tomorrow?