Claudius was hamlets Uncle and later became his stepfather because his mother Queen Gertrude married Hamlets uncle "Claudius".
King Claudius, who also happens to be hamlets uncle.
Claudius killed him.
Gertrude, Hamlets mother.
If this is Claudius in Hamlet, its because he killed hamlets father to take the thrown.
to become king
Hamlet's Uncle Claudius