No, there's no way to hack/unlocked bitcoin wallet/addresses.
But, if you really want to do it, you might find hint for his bitcoin wallet password such as :
1. Password he used on other services.
2. His behavior when make a password.
3. Something that he likes (video games, movie, family, etc.)
4. Looking for paper in his house because some people write down his/her password and keep it secure.
5. Check his PC/smartphone if he uses password manager.
And also sometimes some people has the forms saved in their browsers to be used anytime without typing them again and again, so maybe he can find it in his PC if something like that exists, or if he used a mobile wallet then there would surely be access on his mobile still.
