Gosh....I've just read the article in the Mail. I do believe the parents have a lot to answer for. They appear to have 'learnt' how to be sadistic...shocking.
Sadistic children are caused by their upbringing obviously. The worst bit is being a foster parent and realising you've got someone with problems like this on your hands. You try dealing with this sort of stuff without training and see where it gets you. Foster parents are amazing, but still need time to sort out ways of assisting their charges.
Children such as the two boys concerned in these horrible crimes usually suffer from some sort of attachment disorder...this is caused by neglect or abuse (or both) in infanthood.Their brains are not formed properly and probably never will be.For this reason they will almost certainly be a danger to society for the rest of their lives.