Two things are sticking in my craw with re: Sun, the mother
1. Why is the only photo she shows Kate that of her little girl as an infant? That is odd. No photo at all is less odd than an infant photo of a child who is now a toddler.
2. Sun showed absolutely no interest in Aaron... no warmth.
3. Sun seemed jealous. She was very quick to remind Kate that Aaron is not Kate's child.
So I'm left to wonder...Where is Sun's little girl?
Then again, with her having "witnessed Jin's death" it could very well be that she is still experiencing MAJOR PTSD (sure, all of the six minus Aaron are, but her more so) and seeing the product of her love for Jin may be a constant reminder of that experience.