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.
I must say I'm a little disappointed to find that this one is identified as Fedor sister.
Really? Again - making an emphasise with my disappointment to find that these two plants with different color variation is due as one receive loads of sunlight (sister) and the other cultivated in shade (Fedor) and it's a pity to note that there is no proper reliable source than those who unscrupulously intend to sell the same plant with two different ID.. But Fedor Sister? Really?
Top picture : Mis-identified as Fedor Sister where it receive bright indirect sunlight (too much light actually where you can note burned leaf edges)
This one is identified as Fedor cultivated in indirect light with good shade - the foliage formation is very much in lighter tones with central veins not fully open or exposed with strong coloration. This particular one does not have showy flowers - more like a coined shaped flower buds just peeking through the foliage structure.
Begonia Fedor being a typical Rex Begonia where you can notice the basic characteristics at the underside of the foliage where the have furry red stem with some red tones. Being a Rex Begonia - watering must be administer in full care as not to cause root rot or stem rot - these can be sensitive plant, a slight change in their condition can cause a shock and this one can go dormant or even die.
Eventually I had lost the battle with farming ants with mealy bugs, each time I apply pesticide on it and the ants brings back those mealy bug on the next day had totally devastate my begonia plant. I can't imagine whether the pesticide or the mealy bug that had actually killed my beloved plant.
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.