I don't give much weight to that story. Gossip is a popular thing in the region, it was probably invented there. I have lots of relatives in both Poland and the Ukraine, each one of them has their own conspiracy story.
I think they are each assigned one at birth.
That aside, Keiv has a facinating history, it's said to be the first fortress built in Europe. Part of the main gate still stands.
Still, it's very instructive to see that, even today, your relatives still deal in the ancient ''conspiracies'', or whatever these might be called.
Unfortunately, the only time I've ever visited Russia was in 1971, cultural exchange programme, all that garbage, and was stuck in Leningrad at the university for most of it. Got to see Kiev for ONE lousy day (mutter, grr)