Sons of Indra and Surya
Interesting comparison between Ramayan and Mahabharat
Both Ramayan and Mahabharat had sons of Surya and Indra playing key roles as warring brothers. In Ramayan they were Vali and Sugriva, while in Mahabharat they were Arjuna and Karna.
Vali and Arjuna were sons of Indra while Sugriva and Karna were sons of Surya. Both sets of brothers due to circumstances ended up becoming each others' enemies.
In Ramayan it was the son of Indra who ended up on the wrong side while in Mahabharat it was the son of Surya. In both the cases Shrihari's incarnations played an important role in assisting one brother into killing the other one.