We learn in the final episodes of Mourestu Pirates that
Marika's father Gonzaemon is alive, and goes by the name of Steel Beard, an imperial pirate captain of the Parabellum
But we also learn that Ririka, Kane and Misa also knew this secret, because
Ririka is in the Parabellum crew, Kane switched places with his twin brother, and Misa nonchalantly scolds Kane for the switch.
We can infer that the rest of the crew of the bentenmaru also knew, leaving Marika as the only one in the dark.
Is it so?