Kagayaki said "twins", but Yomi holds only one child. I know that realistically child can just be somewhere else, but since it's a "final page of manga" that specifically made to show their family together, the absence of a child seems very strange.
Maybe is it a translation issue, and she just said "child" and not "twins"?
Edit: Checked the original, and it definitely says twins [双子]. Strange... Is she referring to those two older girls? I thought they aren't twins though...