My Conclusion about the Homolkas...IMHO
After the movie and reading up links about the Homolkas on this board and other verified links, I've come to the more or less safe conclusion that the Homolkas as a whole are a bizarre family.
There is no doubt that Karla is manipulative and a severely psychopathic personality.
They've been shown as a couple who got together with the Homolkas on a regular basis - which makes me wonder how the mother at least or the middle sister didn't realize Karla was being beaten. The most disturbing was how the family had moved on so easily after the death of Tammy (I know, the parents were apparently grieving) but after the entire episode and even eventual sentencing, they're in regular contact with Karla as if things are smooth and normal now. I can imagine most normal families disowning their corrupt offspring.
Then there's Tammy who, also seemed to be bizarre personality who seemed to (documented) flirt with Paul on a regular basis - which probably led to her downfall.
I know its all speculation, maybe the parents and sister despise Tammy but from this pedestal its still a bizarre family.