His father died in a clash with his own brother Untamo, who sells Kullervo as a slave to Ilmarinen. Later Kullervo flees and finds that his family is still alive except for his sister who has disappeared.
Kullervo's father sends him to pay the taxes and on the way back he seduces his sister without realising who she is. Out of shame the sister commits suicide. Seeking revenge Kullervo kills Untamo and his family, only to find his own family dead when he returns home. In the end Kullervo also commits suicide.
Kullervo proved inept and ignorant; having not had a father to pass on knowledge and skills.
The death poem of Kullervo, where he (like Hamlet) interrogates his blade, is justly famous. Unlike the dagger in Hamlet, Kullervos sword replies, bursting into song; affirming that if it gladly participated in his other foul deeds, it would gladly drink of his blood also.