You can add anything you like but once a big pr of cichlids start breeding, they usually beat hell out of everything else in the tank. Bristlenose will probably be fine when the cichlids are small but once they are full grown (about 10-12 inches) they are going to take over the tank and potentially kill anything else you put in there.
If you add some catfish while the cichlids are young they should be fine for 6 months, maybe a year or more. But you will have to watch them closely if they start breeding and if the cichlids start chasing or attacking the other fish, then take everything else out and leave the cichlids in the tank by themself.