The way I interpreted the earlier chapters is that Miko is the youngest of the 3 and the twins, ninja and assassin are older. Also, I can't tell if this was just my interpretation but ninja seems to be the younger of the twins.
@Kyujyu no I don't have the raws either, truthfully I got the spanish one's from Gakusei site and in their version there is a word - Hermanito - for brother that google translated as a younger one. I guess I should've cross examined it in spanish to english dictionary as I did later but it sadly came to mind just now.
Glad to see my ship sailed. I’d kind of been suspecting, but hadn’t been sure how Chroma could stay cursed but the others recover. Pregnancy. Who’d have guessed?
I just wanna point out that there is not a translation error when Chroma says to change them back to normal. Notice how she (I guess she would be the right pronoun given what I’m saying.) doesn’t say to change us back to normal. Chroma likes being a woman.