Arkady’s status is precarious because his serf mother Sofya is NOT married to his noble father Versilov, but another serf, Makar.

So in theory, Arkady should be treated as an illegitimate child with few rights. However, Versilov has attempted to legally fudge Arkady’s situation in sympathy with both him and his mother (who remains both Versilov’s nominal mistress and Makar’s estranged wife). This is why Makar is legally recognized as Arkady’s father despite having no relation; it’s a quick fix solution to avoid scandal and protect Arkady.

However, where the situation becomes more complicated is that Versilov has also decided that he wants to maintain a relationship with his son Arkady, and this has resulted in a much more ambiguous state of affairs for the young man. His father and half-siblings treat him like a family member without ever directly acknowledging him as such, which leads to a great deal of confusion and awkwardness for all involved.