I have a guinea pig named PipSqueak Winchester who doesn't have a cage mate. But he's cage is right next to his older brother's cage Alan the bunny people keep trying to tell me to put them in the same cage is that a good idea or is it dangerous?

Yes it is generally dangerous to keep rabbits and bunnies together because they have a different posture rabbits stand up higher and their legs could easily kick the guinea pig. In general they also have different temperaments and if you really care about them you would keep them with their own species where they would feel more comfortable. Guinea pigs are herd animals and rabbits and guinea pigs are very intelligent

So they squabble with each other or ignore each other that should tell you