Will it help that they've pretty much been together since they were small?
The Kenyi, if male will become phsycopaths when they fully mature. Most kenyi sold in pet stores are male, I think due to hormoning them.
(They will be yellow if male). Honestly, I wish pet stores would stop selling Kenyi. They are not a beginner fish at all. There's plenty of colorful mbuna that are much more suited for the masses.
The venustus might be a problem later.. I don't have enough experience with them to say for sure.
If you remove the Kenyi, you at least have a chance of it working.. With Kenyi, no chance.