Looking on Wikipedia I see that in many of the languages of the former communist countries, namely East European, the North Korean leader Kim Il Sung (or Song) (1912-1994) is called Kim Ir Sen. (I am posting the Polish page because it has more links to other languages than other pages have.)
The difference is not in the family name - which is Kim.
It seems a difference based on the former political divide of the Cold War, as in French and other West European languages, but also in Turkish and Greek (Turkey and Greece already being NATO members at the time), the name used is the same as in English. On Wikipedia I have not found a non (former) communist country that calls him Kim Ir Sen.
I see no linguistic similarity between countries using the same form of the name (Russian, Latvian, Albanian, Romanian share the same "communist" form), so the cause must be politic. But how has been the political divide projected in the name of this man?
To make things more interesting, there are also some exceptions: in former-Yugoslav countries, that is on the Wikipedia pages in Serbian, Croat, Slovenian and Macedonian, he is called like in the Western Europe: Kim Il Sung.
In Bulgarian, which is close if not identical to Macedonian, it's Kim Ir Sen. At least Croats and Serbs use the same name... But not Slovak and Czech, which were in the same country during the communist era: the Wikipedia page in Slovakian uses the "Western" form.
Maybe this differences between neighbours are recent. Are they also political?
The difference in pronunciation between "Ir Sen" and "Il Song" may be bigger in some languages than in others. In some languages it seems big to me (French, Romanian); maybe it's less striking in English... This is even more confusing by the fact that the Kim dynasty includes already three names of presidents all called Kim, a series in which the aforementioned difference might suggest a fourth one.