Understanding the exact source is important here, also. If this cousin wrote down "Minsk, Krasnoyarsk, Russia" on some document decades ago in the pre-Internet age, that could be a good indication that the community in Siberia was really the one being referred to.
If, on the other hand, this was written down recently, then things get much more complicated. What I am especially wondering about in this case is the possibility that the cousin may have copied this information from an Ancestry.com tree. Ancestry.com is set up such that when a user creates a tree, they can enter a birthplace for each person that - this part is key - is partially auto-suggested by Ancestry. If the user starts typing "M-i-n-s-k" into the birthplace field, they will be presented with a drop-down list to select from of various places named Minsk: Minsk, Belarus; Minsk Mazowiecki, Poland; Minsk, Krasnoyarsk, Russia, etc.
This feature of Ancestry.com makes it very, very easy for errors to enter people's trees and then be endlessly perpetuated by other relatives who find those trees: a novice researcher who knows his grandmother came from "Russia", but doesn't know anything about how political boundaries changed over the course of the 20th century, could well see "Minsk, Krasnoyarsk, Russia" in the drop-down list and incorrectly assume that he should choose that one simply because it fits his understanding that "Russia" was the place of her birth, even though that was a very unusual place for a Jewish person to be born in 1836 compared to the city that is today Minsk, Belarus.
