Actresses-sisters Ratna and Supriya Pathak are married to Naseer and Pankaj respectively, but neither the sisters nor the brothers-in-law have ever been seen together on screen.
The actors, who share a cordial though distant rapport in real life, are said to be extremely wary of being cast together.
"I'd love to work with Pankaj. He is a fine actor. But the script has to justify our presence," said Naseer.
Many directors have tried to cast the two stalwarts together, and failed.
Apparently Chandra, who made the critically-acclaimed Bhojpuri film "Deswa", relentlessly pursued the two actors with a hard-bound script and with roles specially earmarked for both actors.
"It was really Naseer Saab and Pankaj Saab and no one else for these parts. The characters they were offered are rare in Indian cinema. The film is a bio-pic and those two roles are rigorously researched and designed. I have been working on the characters for four years. The script is powerful enough to invite the presence of actors like Naseer, Pankaj and Manoj Bajpayee," said the director.
"They have challenging roles to play. I'd like to think they saw honesty in my intentions and were quite taken up by the narrative," he added.