okay so we already know that cuphead and mugman's relationship is really strained in corruption but how is brute's and sinny's relationship I mean are they cordial or do they hate each other as much as the other two (Also I LOVE your au and designs they're all so HOT, and I'd say it to their faces >:3)
In corruption, Sinny and Boris are pretty close because they took each other in. Sinny saved Brutes life, and now Brute acts like a protector/ body guard in return - making sure Sinnys life isn't in any harms way. BUT, it's a little bit complicated with Sinny. He sees Brute as very important to him as well, but he's more "useful" if anything, and he uses Brute to basically survive. So, if something did happen to Brute, he would be very panicked at the idea that he lost a very important weapon keeping him alive.
Then again, Sinny probably could be in denial at the fact that he does see him as a brother/ of importance because the world they are in is screwed.
And losing someone close to you in such a messed up world wouldn't be so great. So, he tries not to get too attached by just labeling Brute as "weapon" in his head.
Again, he could be in denial.