I think they are along the lines of the orchids, but I haven't kept one so I'm not 100% sure.
Years ago I mixed two arabian (neon) dottybacks along with an orchid (all ORA). They mixed fine for me, might have been some luck though. But the neon dottybacks are more aggressive than the orchids and anything new put in the tank the neon would pester (didn't matter what size or what it was).
This is from ORA's website:
P. sankeyi:
The Striped Dottyback is found in the Southern Red Sea and Gulf of Aden. They live in small colonies in rock rubble at relatively shallow depths. This is one of the least territorial of the dottybacks due to its lifestyle of living in colonies with other members of the species.
P. sankeyi have a distinct black and white striped color pattern, and may be a mimic to the Coral Catfish (Plotosus lineatus).
This is an easy species to care for in the marine aquarium, as long as it's provided good rocky hiding places and zooplanktonic foods such as brine, mysid or krill shrimp. More than one per tank is possible since they exhibit colonial behavior and normally do not fight each other. It is best to introduce all the fish together when trying to establish a colony.
Orchid Dottybacks:
In aquariums, Orchid dottybacks are quite easy to keep and feed. They are small plankton feeders so foods such as brine shrimp, krill and mysid shrimp are perfect. Orchid dottybacks are moderately territorial and more than one can be kept per tank, as long as the tank has plenty of hiding places.
ORA actually has a fish called "Indigo Dottyback", that is a cross of Pseudochromidae fridmani x Pseudochromidae sankeyi