Celia and Rosalind are cousins but still they love each other dearly. Whereas, Orlando and Oliver, instead of being of the same blood, are not found of each other.
Rosalind and Celia love each other very much;so much that when duke Fredrick banishes Rose, Celia follows her because she cant stay behind without her.
…if she be a traitor,
Why so am I; we still have slept together,
Rose at an instant, learn’d, play’d, ate together;
And wheresoe’er we went, like Juno’s swans,
Still we went coupled and inseparable.
On the other hand, Oliver treats his brother Orlando terribly,barring him the place of a brother although their father,Rowland de Boys charged him to give him a proper education and therefore Orlando wants to mutiny against this but he does not know how to. But eventually after Orlando saves his life,Oliver becomes a better person when he sees that his brother whom he had tried to kill saved him because he was noble and kind and chose that over revenge.
simple....rosalind and celia are sisters....and oliver and orlando are brothers :P