Cultivars basically come true from seed, hybrids don't. Since Ballerina is listed as a cinereum it would be considered a cultivar and should come relatively true as long as they haven't cross pollinated. But even if some have crossed, that doesn't necessarily mean all of them will. In that case one would thin to type, or remove any particularly interesting offspring to grow on elsewhere.

On the other hand, Phillipe Vapalle is a cross between G. renardi and G. platypetalum, so it won't come true.

Hope this has been of some help.

My Geranium cinereum 'Ballerina' plants are about 6 years old and have never set any seed. I think this cultivar is sterile, as is Geranium 'Johnson's Blue'.

Here is a link that might be useful: Mountain View Experimental Gardens