Can male guinea pigs be housed together?

The short answer to this question is that it depends. If two (or more) males have grown up together in the same family, they can usually live together with no problems, provided they have enough space, and possibly a couple separate food dishes. On rare occasions, you can place two unrelated males together; this is best done when they are very young, or when one is much older and one is very young. Even then, there is no guarantee they will get along. I have had successes and failures with all different breeds and ages of male guinea pigs. It takes a lot of trial and error. I prefer that guinea pigs be housed in groups of at least two, but if one shows too much aggression toward other males, then he must be kept separate.
Right now I have been very slowly introducing some of my single males to each other in a neutral area. I was concerned that Frosted, who lost his cagemate two days ago, would show signs of depression, but so far he has been doing well and seems in good spirits. Because Rodney and Buttons are both extremely timid, I introduced them tonight, and there was nearly zero aggression (Rodney was interested in the tag in Buttons' ear and nibbled on it, but that was pretty much it). I have a very large cage waiting in the wings, so after putting them together for a playdate tomorrow, I may end up having them live together, under close supervision. They will each have their own original igloos, and I will keep their cages ready in case things don't work out. Wish me luck!!