Recovering an account of someone that passed away

A really close friend of mine passed away 2 years ago. Although we aren’t blood related, we were brothers. I understand that doesn’t uphold legally.

My goal is to have his 17yo daughter obtain access to the funds. The only account I know of is through robinhood. Is there any hope without access to his phone or email accounts?

I know this is kind of a shot in the dark. Thanks in advance for any help