All 10 sons of Karna participated in the war of Mahabharata, out of which 9 were martyred .His youngest son Vrishketu survived this battle .Vrishketu's mother was Karna's first wife Vrushali .Arjuna was very fond of Vrishketu .During the war, when Arjuna came to know that Karna was his elder brother, he was sad to kill Karna.When Vrishketu also became helpless in the battle, Arjuna helped him .Arjuna helped Vrishketu to flourish and also taught him.At the same time, Vrishaketu was also made the king of the country of Anga.Vrishketu was very dear to both Arjuna and Lord Krishna.B. K. Shivani's Tips for a Calmer, Positive Mindset