The killer of the kids is killing the kids to take the heat off of Seward. If similar killings are going on, then people will doubt Seward's guilt.
As one of them (can't recall who) said...the perpetrator is going after hooker street kids because he thinks no one will come looking for them anyway.
Kallie's mom = Seward's sister.
The boy is Sewards nephew. Seward's sister killed his wife. Seward is protecting his sister - and her son. His sister is trying to get him off death row but pulling copy cat crimes. Maybe she is in partnership with someone...a man?
just thinking out loud...