i am writing what i found in various contexts,not according to skr.as ram-sita,the other 6 siblings of them also sacrificed much,so i am trying to make analysis on all 4 pairs.
Ram-Sita
perfect in all terms,an ideal for their siblings,they proved to be ideal and told how an elder brother or sister should be so that their siblings can follow them.
Bharat-Mandavi
not according to skr,but what i read,i am telling,bharat and mandavi are a reflection of what sita-ram are.according to their nature,bharat and mandavi are calm and composed,cold-natured just like ram-sita,when ram left for exile,bharat stayed in nandigram and mandavi stayed in ayodhya both living a vanvasi life,sacrifice for their siblings,seperated from each other.
Lakshman-Urmila
not according to skr,but what i read,i am telling,lakshman and urmila are a shadow of what sita-ram are.according to their nature,lakshman and urmila have a fierce personality in comparision with the other 3 pairs,seperated from each other,sacrificed for their siblings,living a vanvasi life.When Lakshman went for exile along with Ram-Sita,Urmila stayed in Ayodhya.Urmila and Lakshman stood for their siblings and are more attached to them in comparision with other 2 siblings.
Shatrughn-Shrutakirti
we can say they are follower or pagchinha of sita-ram,they are characters full of life and laugher.when sita-ram went for exile,it was Shatrughn-Shrutakirti who looked after state-affairs just like king and queen,they lived a unconsumunated married life just like their siblings.this is what a follower is called.