why would a good God let this family and this 15 year old suffer like this
You asked. So.
Everything that happens, happens because of necessary and sufficient causes. The only way to prevent a single bad thing from happening from happening is to break the chain of cause and effect. To stop every bad thing from happening, God would have to stop the whole process of cause and effect: not just breaking the "chain" at one point, but breaking every link.
I'm thinking God could effectively prevent all bad actions and consequences by redesigning us as robots,and then prograzmming us so there could be no bad choices: in fact, no choices at all, good or bad. Everything would go according to His will, because He alone would be the only Being in the Universe with a will.
In your opinion, would that be better for us, humanly speaking?