If you can provide a bit more detail, we might be able to help further. Did the passenger record give a place of origin or the name of nearest relative in Russia? What are the ages of Ludwig and Carl? What religion did they practice? Any other seemingly inconsequential detail may help.
Russia is a huge country and was even bigger pre WW I so more detail might help us to narrow down the location. My best guess based on where they settled in SK is that they were from Volhynia, today northwestern Ukraine.