Count Reichsin is initially a vassal of the Kingdom of Rhodoks.
You may fight him or have him side with you as you help Lord Kastor of Veluca, the corresponding claimant, overthrow King Graveth and gain control of the kingdom for Lord Kastor of Veluca.
Note: Certain aspects of most NPCs are randomly generated at the beginning of every new game; these include all family lines (other than the parents and siblings of younger NPCs or spouse and children of older NPCs), personalities, and initial fief ownership.