So do you guys think it's a good idea to tell his parents about it ? To search of they find some twelve words it's a key to some hisen coins ? Or what do you guys think?
It is a good idea to tell his parents, however, it's much better if you are the one who will assist them on finding the private keys of your friend's wallet. You can do it some other time if you have enough time and can fly to your friend's country, it can wait actually instead of letting them or someone close to their house does it.