question

Technically Ivan and Alyosha have the same mother and father. Dmitri has the same father ( Fyodor), but another mother. The next brother is considered Smerdyakov. It is not proven, but it was said that Fyodor either raped or seduced Lizaveta, a retarded mute girl. He is considered their half-brother, but no one is sure, and Fyodor does not care to even consider him his son.

Smerdyakov is the illegitimate son...there are 4! brothers

The top of this site says there are 4 Karamazov brotheres. Aren't there just 3 brothers, and then the father? I'm only a third through the book...so...unless a 4th brother appears later on, I believe there are only 3.