So I want to tell his parents about it as probably his private keys is saved in his personal PC or email or his phone or some paper
If your intention of telling your late friend's parents is to enable them discover and retrieve the stocked Bitcoin, then go ahead and do it. It's a noble thing to do. However, if it's the other way round and you want to harvest your late friend's Bitcoin since (according to you) his parents are noobs who don't know jack about Bitcoin, then it's wrong. Don't profit from other's misery.