This may seem odd, but bear with me.
People find other people attractive, but often find gorillas ugly, but then then find cats beautiful. The reason is that gorillas are pretty similar to humans and thus are seen as "ugly humans" and not as separate creatures as are cats.
With neighboring nations, it is often the same thing. When Poles were in power, everything was to be Polish with others being "flawed Poles" or just "incomplete Poles" etc… no surprise that when Russia became mighty, the same thing happened just from a different side. Henryk Sienkiewicz ended With Fire and Sword with the line, "Hatred poisoned the hearts of two brother nations." Brothers will never be the same, but good brothers show respect and honestly try to cooperate in any way that they can.
In a broader sense, this also applies to Slavics and Germanics. We've been neighbors for over 1000 years.