What references? Sam and Max barely show up in 302
And like Avistew said, people who are raised together from a young age are less likely to become sexually attracted to one another. It's called the Westermarck effect. Sam and Max have apparently known each other from the time they were very young, so I'm guessing it's just a bosom buddies kind of a thing. I don't think either of them has nearly enough emotional maturity to have a romantic or sexual relationship.
I think that's one of the things that makes them so charming, in spite of the wanton violence. They act a lot like kids, and there's this quality that they're just "playing" at being detectives. Max is a psychopath, but he's also naive and super cheerful. Sam is a little more aware of how to deal with people, but he's still pretty self-centered himself. Sort of like how a small child can empathize with others, but not necessarily sympathize. They'll understand from your voice and body language that you're sad, but they might not be able to understand why.