Guinea pigs and rabbits should never be kept together: rabbits are carriers of a bacteria (Bordetella bronchiseptica) that doesn't make rabbits sick, they just live with it, but can easily kill a guinea pig.
Rabbits often injure guinea pigs even when trying to play, because they are bigger, stronger and have a different body language.
And last but not least: rabbits and guinea pigs have different dietary requirements.
image by Speak-up Guinea-pigs