I'm writing a novel set during World War II in Russia, but I know little about naming or the language. I've gotten so far that Russians don't use full names with people they know or informally, but I'm having a difficult time figuring out who would use what diminutive.
My main character is Svetlana. Her nickname is Sveta but I know there are also other diminutives for her name like Svetushka, Svetka, Svetulya, or Svetukha. Which one would her brothers use? Her mother? Grandparents or other relatives? Or what about friends or boyfriend?
Also, what about the names Yuri or Nikolai? I know the diminutives for both are Yura and Kolya, but what other diminutives would be used for them? I've done a lot of research but I can only find so much information.