Scanlan was the first person to whom Grog told his concerns about Craven Edge, and Scanlan advised Grog on what to do about it.
Grog was deeply affected by Scanlan's death at the claws of Raishan. His first reaction was disbelief, which soon turned to anger as he shouted for the rest of the party to "FIX HIM!"
Grog participated in Scanlan's resurrection ritual, where he removed the Titanstone Knuckles and Belt of Dwarvenkind and placed them on the altar alongside Scanlan's body. He then spoke to his friend's body lying before him.
You've been with me through so much. I pride myself on my strength, but as we fought Earthbreaker Groon, you were there by my side as I learned that my true strength comes from my friends. Which means that these trinkets, no matter how strong they are...mean nothing. You knew me before them. And I would hope you would know me after. And while my best buddy Pike taught me to love, you taught me to laugh. And I don't wanna know what life is like without that. You've spent so many times inspiring me...I'd like to take a page from your book.
Grog was saddened by Scanlan's departure from Vox Machina, but out of the entire party, he was the most understanding and respectful of Scanlan's decision, even going so far as to apologize for not getting to know Scanlan's history better, while opposing any attempts by Vox Machina to try and convince Scanlan to return prematurely. Despite this, Grog misses the gnome greatly, frequently visiting brothels and buying services for two, only to remember that Scanlan wasn't with him anymore.
When Scanlan finally returned after over a year, Grog was furious with him, speaking no more than a word to him, and leaving whenever Scanlan attempted to talk to him. Scanlan was later able to make it up to him (more or less) with an apology and a blank check to every pub in Ank'Harel.