Light Novel - Ascendance of a Bookworm

Once Hildebrand finds out about the adoption and engagement, he might plot to make book addicted Dunkelfelger demand that Rozemyne should be given the throne as the true Zent and she should marry someone who loves her instead of becoming a third wife in a purely political marriage. There's two years between adoption/book acquisition and the marriage.

Obviously he'd be pretty heartbroken when the plot works, she marries Ferdinand and arranges for Hildebrand to be sent to Ehrenfest as first husband of Aub Charlotte.