THE BIG F Q IS THE EMPRESS DUKE DAUGHTER OR NAH???? PLEASE SPOILER ME

my theory is that that white haired knight is the empress half brother that got hidden at birth and that the empress's father misunderstood everything about his own son's birth. but it's just a theory

Astelle is duke Reston's daughter. Fritz is also the duke's son. The child whom Jacqueline was carrying when she was still Ecklen's lover has never been born. The knight is Ecklen's adopted not his biological son