It would be very difficult to think of Ukraine as being anything but Russian. The capital of Rus was moved to Kiev by Prince Oleg of Novgorod (around 862) where Vladimir the Great started the baptisms of Kievan-Rus and established ties (mostly due to his marriage to the Byzantine Princess, Anna) with Byzantium where Russian laws were ceated and the Slavonic and Cyrillic alphabets were invented. And even if all that happened in the Middle Ages, you can see what Russia was from 1533-1894.
In 1533, despite the Mongol invasions and the Lithuanians, the Russian border was still near Kiev and the NE borderlands ("Ukraine") were part of Russia (including Kharkiv). Poland and Lithuania were controlling the rest of the borderlands at that time.
Between 1533 and 1689, Russia expanded till Kiev was on it's border. And between 1689 and 1801, even the Western borderlands became part of the Russian Empire.
So my question is what is a Ukrainian? Are they the people that Prince Oleg of Novgorod conquered? But even if they are then how could somebody prove they are a Ukrainian and not a Russian? I mean mixed marriages do happen.