How did society react about and approach identical twins in Europe, mainly around the 17th century?
I think it's safe to say that they were regarded not that differently than they are today. An easy example is Shakespeare's A Comedy of Errors, from the beginning of the 17th century. That play revolves around twins being mistaken for each other. The comedic part of that isn't of concern to the question, but the fact that the play treats the characters as just people, and the other characters in the play treat the characters as "normal" when their twin status is revealed in the end is very strong evidence that nothing disturbing or supernatural was seen around the mere fact that people were twins.