These girls' little brother should be the next emperor, and it's about time they know it. As Jahanara's nearly grown granddaughters, Gulbadan and Rurayya are finally learning their true family history while sitting on a boat with Nizam:
Behind our craft's bow sit my two granddaughters, Gulbadan and Rurayya. No longer girls, each is a wondrous incarnation of my daughter. Looking at them, I think that time has moved too swiftly, that just yesterday I was stroking the soles of their diminutive, untested feet. My love for my granddaughters is even stronger now than it was then. When I see them I feel as if I'm moving forward into places harboring no regrets, no memories to remind me of my scars, those thick welts upon my mind and body. (Part I.4)
They're eager listeners to their grandmother's story (wouldn't you be?), and thus they serve a specific purpose in our book—they're almost stand-ins for us in the audience. They're learning everything for the first time, just as we are.
By the way, what will these girls do with this new information? Come on, Shors, let's have a sequel.