There's a lot more to this story. The 20-year-old brother came home. Remember mom is 34. Soooooo perhaps one of the "dads" committed this crime. Here's a link to the Daily Mail article: http://www.dailymail.co.uk/news/article-2880061/Eight-children-dead-Cairns-home.html
Reading between the lines it seems now that the mother is also a victim.
Sometime UK Daily mail get the story before anybody