This novel presents some amount of suggestion that circumstances control us and not the other way around.
We can describe this notion in the broadest terms as a Nurture over Nature novelistic scenario.
Though there is quite a bit of exploration into personality differences (as the novel looks at the ways Ivan and Alyosha differ from one another and from Dmitri despite the fact that they each share the same basic background story), we also see a large degree of weight placed upon the notion that people cannot escape themselves.
They are who they are. And they become who they are as a result of the circumstances of their birth.
This idea seems to play into the notion that Smerdyakov cannot be held solely responsible for his crime because he cannot be held responsible for the circumstances of his birth, his life, and his character.
The world has made him.
I think that you are right, to a certain extent. Clearly, although there was only one murderer in the story, the other characters, especially the second son, is forced to realises his own part in the death of his father. This novel paints a complex moral scenario where guilt is something that is shared and not owned by one person alone.