Unacceptable
As much as it pains me to say it, I'm with Gray on this. Digging up and emailing a relative's death information (his brother's Find a Grave memorial) crosses a line. There is zero justification for sending this to someone, no matter the online drama.
While he's blaming this on generic "trolls," Gray has detractors across various platforms - including Twitter and the newcomers to his channel that he frequently attacks. One has to wonder where this person came in contact with him, what their motive was, or if the whole thing was manufactured just to gain sympathy.