I'm sorry, but I'm not specifically familiar with a story named 'ek ishq ek junoon'. It could be a relatively niche or regional story. You might want to check local libraries, cultural centers or online forums dedicated to the relevant culture for the full story.
As I don't know the actual 'ek ishq ek junoon' story, I can't say for sure about the characters. But generally in a story with a title like this, there might be characters who are deeply in love. There could be a protagonist who is driven by their love (the 'ishq') and perhaps also by a strong passion or determination (the 'junoon').
It is indeed based on a real story. The creators of 'Sirf Ek Banda' took inspiration from actual incidents to shape the plot and characters, giving it a more authentic feel.