Shri Radha and Shri Krishan are substantially a single entity behaving as two for the sake of their Divine pastimes. As an ordinary lens of a camera can capture only the outer surface but an x-ray detector reveals about the internal structure, it is a devotional insight which enables us to genuinely visualise their indistinguishability. So saints try to explain the relationship of Yugal Sarkaar through various aspects, four are presented here -
1) Shri Radha is primarily known as 'Mahabhaav' - the extreme love/ an unquenchable thirst for Lord Krishna, who in turn is the epitome of 'Ras' - the bliss. Thirst exists just to have ras while ras has little value in the absence of thirst. So both of them are integral to each other. They live in constant union yet feel the pain of being away due to their ever growing love.
2) Shri Radha is also considered as the soul, internal potency of Shri Krishna. Just like Yogis experience bliss in the company of their inner self, Shri Radha Krishna take delight in each other. Often a question is raised - why did they not get married? For this one must understand that marriage is a social custom to bring two beings together. How can anybody marry his own self?
3) It can further be viewed as a wave repeatedly rising up and then merging back in the ocean. As wave can not be separated from its source, Shri Radha and Krishna are inseparable too. Liquid mercury is also seen breaking into small droplets and restoring multiple times in a closed container. Likewise, the unified form of Radha Krishna splits up for their mutual pleasure, yet remain one. Their dual appearance embodies love in its purest form which extends beyond physical dimensions and hence question about marriage stands inapplicable. Nevertheless, due respect is paid to the holy belief that Brahma ji officiated their wedding ceremony at an early age. Perspective of all the devotees is always meant to be venerated.
4) From scientific point of view, Shri Krishna can be taken as element and Shri Radha as energy. For that reason, it is said that Shri Krishna can be easily attained through the mercy of Shri Radha as energy only makes the element active.