Bollywood industry works like a relay race where the baton of creative hands is exchanged and is passed through generations. Not necessarily within a film family, it can also be true for talent which is not even related.
For example all roles that Irrfan Khan used to get couple of years ago, started going to Nawazuddin Siddiqui and all the roles that use to go to Nawazuddin Siddiqui now go to Sohum Shah.
As actors mature and progress, they look for new excitement and challenges in their characters. Interestingly what Irrfan would have like to do 5 years back was passed on to Nawaz and now Sohum. All of them are known for their unusual looks and acting prowess.
While Irfaan is now excited with more mainstream cinema, Nawaz seems to be leaning towards edgier characters and Sohum is getting attracted to characters roles that allow him to showcase his talent.