I'm not a parent of teenagers but I am a high school teacher. The behaviours you are describing are quite unusual for their age. With what you have available at your house and they don't want to use it is pretty odd. When you speak to their mum, mention that at their age they things they should be doing. Maybe ask if anything was mentioned at their schoool as the teachers would have noticed their behaviour. I'm sorry I can't help with any more... good luck