One interesting way to start out might be to have them fighting for the claimant with the least legitimate claim. A powerful Duke/Duchess with a very tenuous claim to the throne. That lets us start simple but leaves plenty of room for an heir/heiress and whatever else we want to introduce later on.

Also, hi [@GreivousKhan]! Good to see you! It's good to be back on RPG after an unwelcome hiatus.