Garrett so hated Greed (and yet kept coming back to that awful place). The man has his uses though. Garrett isn't into physical touch a la canon showing us how much he literally dodges it but. but. but if he can develop feelings then that's a start.
Also ngl sometimes I imagine Garrett getting close to Stocke because that was his favorite person and then that leading to things. And then sometimes more things with Stocke and Greed. (Or maybe Garrett gets jealous of Stocke getting close to Greed and it becomes a Thing with the outcome being the only peaceful solution is a threesome.)
LOL SHIT I MEAN there's a lot about Greed to hate let's be real here. Greed doesn't really care who fucks who (he'd be a hypocrite otherwise and he's not down for that). But he also wouldn't say no to a threesome or just fucking watching Stocke and Garret go at it while he just kicks back, smokes, and drinks because he's an awful creature
But, he was never betrayed and while dealing with Greed was a hassle... he knew how to give Garrett what he wanted/needed so. He put up with him. They were definitely allies and I think if push came to shove Garrett would have defended Greed.
Greed is asshole incarnate and the fucking worst. But he would definitely just slide on it, take a seat. "Don't stop on my account."