Four brothers?

The précis of the novel at the top of this page states there are four Karamasov brothers. However that assumes a certain not uncontroversial reading. The narrator never explicitly states that Smerdyakov is Fyodor's son: it is offered rather as a possibility or a 'rumour' by the narrator. Readers may find it probable, but it remains unproven (even though, as Fetyukovitch would have it, it makes for a good romance). I'd suggest that it's part of the structure of the novel that there is always the shade of unreliability about the narrator's version of events. We're never quite allowed to be certain what happened by the window on the dark night of Dimitri's flight because we can only be certain about Smerdyakov's version of events as experienced by Ivan while we have a similar faith in Ivan's experience of the Devil's existence. Accept the Devil's existence, and then we also who know whodunnit, because we're implicitly accepting the narrative conventions of the genre, just as Alyosha would have us the 'narrative conventions' of theology: i.e., religion. But perhaps that's one fiction too far. Give back that ticket, as the rational Ivan urges, and you're left in a world without laws, be they narrative or moral, and perhaps without objective truth. That's a world where certainty of knowledge may not be attainable. That's a world in which all the certainties of narrative convention are usurped. And that's also a world in which there are Three Brothers Karamasov, not four.

There are four brothers, and the fourth one killed the father.

There are tree legitimate Karamazov brothers, but there are four and we hope that the fourth one killed the father

I love your post and just started a new thread on this very issue. the narrator's voice is of a town gossip and you're right, nothing is known for sure. We accept what he says as fact, after all, he says he's writing a "biography". But it's a story that took place 13 years ago and some of the "facts" don't exactly ring true.

I have my doubts about the fourth brother. The narrator mentions that there was a criminal in the area on the night he was conceived. Everyone just assumed Fyodor did it but no one "knows". I think it is an amazing assumption, based largely on the beastial Fyodor's kindness to Smerdykov. If he really is not the father, what an amazing thing he has done, to take responsiblity for this boy, send him to cooking school, etc. This book is mind-boggling.