So let's say you killed, for example, someone who has a relative who is a lord. Then that relative will be very, VERY angry at you, and will try to chase you no matter what the army difference is, unless that relative just disliked his killed brother. He wouldn't hate you as much, but will still try to look for you if in battle.
Let's say you killed someone without a relative who is a lord, but who has a son. That son will take a couple of years to get into the game because of age reasons and his dad not there directly. But when he DOES grow up without his faction eliminated or him assassinated, he will be an eager young boy (15?) looking to avenge his father. His priority of destruction will be:
1. You.
2. Your friends.
3. Your vassals.
4. Your faction.
5. His dad's enemies.
6. His faction's enemies.
7. Bandits.
Is that what you're trying to imply?