I think, sagar's never planned to show PRC & Sanyogita's love story with RT - MC, I mean at 13. Even koteshwar yatra & Someshwar's death - all was planned to be shown by Angad....because, Jas said in one of his interviews that "he doesn't mind sharing the screen with Angad"
So, they showed PRC to be 7 when Sanyogita was born....so that, they can add the payal giving... & stuff sensibly. It's just Maker's imagination....I don't think there was 7 years of age difference between PRC & Sanyogita (Lakshmi may clarify us on this).
If Sagar's would have known that the serial will shape up the way it is today with PRC-RT, I am sure, they would have shown a 3/4 years difference between them.
Thats my guess 😳 ....MAKERS make it sensible/good 👏 or 😡