The unwritten rule is that every Bollywood period film must have a love story as its axis.This has been going on from the time of Mughal-e-Azam and Amrapali.This is fine if there's already a romantic partner as in the case of Jodhaa-Akbar. Plus Akbar's biography was already available from which the director liberally borrowed to add enough details to make the film authentic.
Now the problem with this rule is that certain historical figures have had no love story. Then the filmmaker will attempt to shoe-horn an imaginary love interest or elevate one of his wives/mistresses to a dependable love interest. See Ashoka. This often comes at the cost of misrepresenting the core of the character. Note how Bajirao was degraded to a sulking lover boy who refuses to go to war because Mommy won't accept his lover.
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