I get the impression that VT was a bit of a loner (per the neighbour) as a child. We know that he is very bright. We have also heard (not sure if this is true) that his mother was an agoraphobic. His next older sibling is 10 years older and the four older children are grouped together in age. I don't consider it all that unusual for an exceptionally bright child to be more introverted or to spend time doing activities at home rather than playing with other children. The parents are responsible for arranging social activities and ensuring normal socialization at an early age. It's possible that with the four older siblings VT fell between the cracks, or that he was spoiled, indulged and babied for too long.
I see parallels with the Scott Peterson case. We had the same situation where Scott was a bit of a loner and didn't socialize with other children. His mother took him to work with her and I got the impression that he was kind of ignored, but managed, as a child; that he was babied, indulged. We heard that he didn't need to learn how to walk because his siblings carried him everywhere.
There's a connection that I'm seeing between parents that, for whatever reason, don't engage with a child in the very early stages of development. We saw it in video footage of Casey Anthony with her daughter. Cayley was trying to interact with her mother, but Casey was miles away. Eventually, it seemed like Cayley was miles away too. It's my understanding that when a young child attempts to engage with a parent and is contiually ignored, they learn to suppress not only their natural desire to interact emotionally with others, but they learn to suppress the disappointment they feel when their efforts are ignored or neglected. This is where these children begin to cut off their own emotional responses ... where they first stop feeling. As adults, they lack empathy for others, but still feel sorry for themselves.Given what I understand of the premeditated attack on Joanna, I don't believe that VT had any empathy for her. He must have sociopathic tendencies to have carried out such a calculated attack on someone he didn't know.