One story could be that two sisters were in a play together where they had to wear very minimal clothing for an artistic scene. They were initially nervous but supported each other throughout the process. They learned to be confident in their own skins and with each other's presence. This experience brought them closer as they overcame their shyness together and it became a memorable 'naked sister story' in a sense of being exposed but having each other's backs.
There was a pair of sisters who went on a beach vacation. They decided to take a moonlit walk on the beach in their swimsuits which were quite revealing. They talked about their dreams, fears, and future plans. The openness of that night, both in terms of their conversation and their state of dress (being nearly 'naked' in a sense), was a beautiful moment of sisterly connection. It was like they were baring their souls as well as being physically exposed to the elements and to each other.