Harvey is one of those characters from Nuka-World.

Harvey is a long time Nuka-World resident. Harvey has lived there with his family since before the Raiders took over the park. As a trader, with his family now killed, he considers the other traders his family. 

We meet Harvey at the transit center, hurt or so he tells us.

Harvey will tell us anything. Some choose to kill him, I have in gameplays. I had also kept him alive. Killing him will lead to no other interactions, surprise! Keeping him alive you will run into him in other places other then Nuka-World.