I know religion usually the most absent thing whenever the story revolves in Soviet Union. But when remembering Alexandrov family are devoted Orthodox who has to hid their belief forever, I think religion is still worth to be explored among my OCs. Just as reminder that each people has their own religious (or non-religious) journey... but I'm not planning to make it as full personality since they still live in Soviet Union. Therefore, the list below was only based on my 2013 imagination that transliterated.
Dmitry: Agnostic. His mother is Orthodox but never force one, and later Tatar family who are Muslims never force too. Dmitry decided to not choosing any religion but believe beyond force)
Alexei/Vitaly: Orthodox, later Atheist after the trauma, but still remembering the liturgies
Vadim: Orthodox, not religious after the trauma
Vasily: Atheist, then secretly Orthodox after married Elena
Fyodor: Orthodox, later Atheist during abuse, and back to Orthodox after war
Anatoli: Rodnover, not so religious but still hid his belief
Oleg: Orthodox, hid his belief
Semyon: Orthodox in youth, then Atheist for entire life, then Agnostic after Veronika's death
Stepan: Believe both Protestant and Buddha because his parents has different religion. But he become not so religious while still working at ensemble. Later fully embraced both religion when allowed to go home at 1945.
Ivan: Orthodox, hid his belief
Andrei: Orthodox, hid his belief during working and Maxim's abuse, then embraced again after war
Maxim: Orthodox, later Atheist after the trauma