They will be fine together for a while, are you intending to keep the Capensis growing or give it dormancy for the VFT? If so they will be fine till dormancy, and you can separate them in spring.
As to what it is, you cant be sure till it matures a bit and even then it is not good to give it a name without being certain its parentage, as they can exhibit some of the traits of named CVs but not be that plant at all, which can cause chaos if swapped, sold or bred from, just label it as a NOID. Its probably a stray seed from the nursery plants, that has germinated in the pot.
Good luck with the plants.
Cheers
Steve