Begonia Fedor does have many similarities with so many other common varieties, especially with 'Silver King' and 'Voodoo Star'. I can really tell them apart unless I align them together to note their slight differences.
There are many confusion as their foliage tend to morph with the variation of shades and colors depending on how much light it receives on its foliage.
There is a slight lavender tones at the edges similar like Begonia 'Fireworks' - I think these cultivars are interbreed and their dormant characteristics are showing when they are growing.
Here is the link where I had put together a list of all the begonias that I had come across. A database of all the different types & their characteristics. Please click on the link on the title above for the post.