After Sita vanished into the earth, all that remained were blades of grass.
Overwhelmed with grief, Rama caressed the grass, thinking of the past.
He then embraced Lava and Kusha, acknowledging them as his sons, princes of Ayodhya.
Later, Rama secured kingdoms for the sons of his brother Bharata, and likewise for the sons of his brother Lakshmana.
Following Bharata's advice, Rama declared that his own sons, Lava and Kusha, would rule Ayodhya after him. Legend reports that Lava founded the city of Lavapura (modern Lahore), and Kusha founded the city of Kasur to the south of Lavapura.
Inspired by: Sita: An Illustrated Retelling of the Ramayana by Devdutt Pattanaik
Notes: This story is on p. 3 of the book. Pattanaik includes the detail about the grass. The story is also found in the Uttara Kanda of Valmiki, sarga 108. Sita calls Bhumi by the epithet Vasundhara in Valmiki's text. When Rama takes the twin sons "home," he means to the palace; previously, the boys had lived with Sita in Valmiki's hermitage.