Yudhisthira performed the Ashvamedha Yagna to unite Bharatavarsha after the Mahabharata war, resulting in Babhruvahana killing and then miraculously reviving Arjuna. The ceremony concluded with the tale of a golden mongoose, illustrating selfless sacrifice over material offerings.
Post-Mahabharata, Yudhisthira rules and performs a Yagna. Parikshit becomes emperor, killed by Takshak. Janamejaya, seeking revenge, starts a snake sacrifice, which is stopped by Astika, preserving snake lives.
Plenty of things happened after the Mahabharata war. This post covers the story of Parikshit and Takshak snake.
Lord Rama had 2 sons but Devi Site gave birth only to Luv. Read this folk tale to know where Kush came from.