But is it good to contact his relatives? All the money goes to his wallet, if his family members don't know about it, how can they get it? They need to own his wallet or private key to get them, Bruno must let them know beforehand, otherwise our contact will not effect

Okay, take it a bit further.
Do you think Bruno asked for donations, just to see them get wasted for ever?
How about the scenario were a friend or a lawyer turns up to his daughter's doorstep - in many years from now - with our donations?
I believe we
should not contact the family, but respect Bruno's final wish instead.