Back when first time writing in 2013, I imagine what languages that my OCs can speak in real life. Of course in the story, it will be fully written in English. I am not a polyglot, hehe.
Dmitry Petronov - Russian
Alexei Mikhailov / Vitaly Bodenko - Russian, Ukrainian
Vadim Oktyuchev - Russian, German
Vasily Nandev - Russian
Fyodor Rokossovsky - Russian, English
Oleg Sepnenko - Russian, Ukrainian
Anatoli Cheyko - Russian, Belarussian
Semyon Isayev - Russian, German, Polish, French
Andrei Fatanov - Russian
Stepan Tabanin - Russian, Sakha-Tyla
Ivan Koshchin - Russian
Maxim Laruskiy - Russian
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Additional Notes:
1. Fyodor speaks English because he reads a lot of English book too. Usually from the thrift store or black market store, where he can get old worn out book that nobody looks for. His coping mechanism when smoking is not allowed... is by buying all kind of newspapers available and read nonstop. To make himself busy and invisible from his family (unless he has to shield his brothers).
2. Semyon speaks 4 languages because... he's been living for hundred years and travel a lot as a nobleman with magic power. If someone had long lifespan, wealth and magic but cannot even speak more than native language, it's... pathetic. Also Semyon mostly use that language to blend better with locals and get lovers in the past (before settled in 1919 with Veronika and become widower in 1928)
3. The letters between Stepan and his family members are always written in Sakha-Tyla, and it was the only thing that makes him remember his roots.
4. Vadim speaks German because his family used to speak German as second language. Despite he was neglected and abused by his father, he still demanded to learn German just like the other siblings.
5. Anatoli also speaks Belarussian because his fiancée was a Belarussian.