:
What we think happened is that the boys had a pile of clothes in the corner of their bedroom. Pigs they are. Anyway these clothes were right next to the glass sliding doors and the sun shines down right through the window. I think it is called a combustion (thermal) fire but I'm not 100%. There was nothing else there that could have caused the fire. No electricals or anything.
So for people who leave piles of clothes (that they're hiding from their mum) next to glass door's beaware. It can and does start fires !!
So we aren't 100 % what exactly caused it but this is the best we can work out.