Rama did not exile Sita willy nilly.
The dramatic description of exile of Sita, we are so familiar with is the work of Kalidasa not Valmiki in his magnum opus Raghuvansham.
In Critical edition:
- Rama sent Sita with Lakhsmana telling her that she will be staying with Valmiki, friend of Dasaratha, so he is like her father-in-law. Ahalya was there to look after Sita.
This was no wild abandonment of Sita in the forest. Rama and Lakshmana kept an eye out for her.
The day Sita was to deliver the twins, Shatrughana had reached the Valmiki Ashrama and congratulates Sita and welcomed the twins. He then reported to Rama about the birth of his sons.
Shatrughana then leaves for War with Lavana and conquered Mathura.
(Lavana was son of Madhu Yadava and nephew of Ravana. Lavana’s descendent Soora got the Mathura throne back many years later.)
In the subsequent fourteen years, Laxmana and Shatrughana’s older sons looked after and trained Lava and Kusha.
14 years after Lavana’s defeat, Shatrughana while returning from Mathura, in his regular annual trips, again as usual stops as Valmiki Ashrama, he does that going and returning from Ayodhaya to Mathura every year.
He takes the top officers and they go and meet the young princes and hear Ramayana from them.
Ramayana was already known abroad and was not limited to Valmiki Ashrama is a conclusion from this.
Second conclusion is if not the main population, (most likely them also) but all officers knew that Sita is sheltered at Valmiki asharama, and she gave birth to twins and they were being brought up and trained.
Later Lava Kusa will sing Ramayana to Rama and the court as well, 20 sargas a day, this takes up more than a month. Imagine your little children have gone to city and not returned for a month and mother Sita would not be worried!. That means Lava and Kusha visited their father regularly and stayed with him.
The Manmohan Desai effect of lost sons united after many years is the work of Kalidasa, not Valmiki.
The subsequent capturing the Ashwamedha yagna and twins defeating their uncles and cousins becomes an exercise in demonstrating to people, the ability of the Twins to succeed a King like Rama.
The abandonment of Sita and emotions we feel and the so called hiding of twins is the Kalidasa’s dramatic doing. Not Valmiki.
Dasaratha curse, Story of Sita and Crow and content of message of Sita to Rama are three sections which the critical edition frowns upon. When Sita returned to her mother Earth, Rama‘s anger and threat, those 56 verses are definitely interpolations or several portions of those verses.