I'm afraid rabbits and guinea pigs should not mix. They are different species and will have no benefit of living together, they have different ways of communicating so cannot communicate with eachother. They also have different dietary needs, for example guinea pigs need high amounts of vitamin C as they cannot produce their own whereas rabbits can. It is very dangerous to keep the two species together. One hop or kick from a rabbit (either intentionally or accidentally) could easily kill/harm a guinea pig due to the very different builds. Some one I knew kept a rabbit and guinea pig together and the guinea pig was accidentally killed by the rabbit just through one binky from the rabbit catching the guinea pig. Rabbits also carry a bacteria which if passed onto guinea pigs can be deadly. So no, rabbits like rabbit company and guinea pigs like guinea pig company not mixed.