Humphrey and Irwin were not homosexual as Vykkers don't have a concept of 'male' and 'female'. All Vykkers are hermaphrodites (they are both male and female in one). This would explain their sexual ambiguity, in particular their campness: they sound like male but behave like females.
However hermaphroditic animals in our world (eg worms) still need two of them to reproduce (one to provide sperm and the other to provide the eggs). Vykkers are self-impregnating (check the oddworld universe if you dont beleive me) but I suppose they still like the companionship of a 'significant other', which would explain Humphrey and Irwin's relationship. I remember a quote from somewhere that described Irwin as a famous scientist and Humphrey as his... "friend"; which sounded a bit suspicious at the time but made sense once I played the game.
ps I wrote some of this stuff in a different thread when people were talking about Humphrey and Irwin's possible homosexuality. Obviously noone read that post as the same people were here discussing the same thing all over again.
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