I'm with Stella on this: the little sister's eyes are a bit dark and could do well with a bit of selective brightening. And I personally might consider brightening the twins' irises a tad, too, to make the eyes look more expressive.
There is a green cast there ... I guess they were standing on your lawn for this to be taken? And that reflects off part of their skin. You might want to correct that?
It is framed a bit tight, but that's ok.