My last 2 kings have died in battle after having 1 son, so I have no close relatives. And I think that Jimena no longer controls any of the Spanish kingdoms. Barcelona took Aragon, and I matri-married the heir a couple generations ago. Navarra is huge, having taken most of Portugal, though Portugal is still a Muslim nation. I think my kinsfolk also have Denmark, but they are a 3rd cousin or something. I would have preferred France to Byzantine, but the French have 0 daughters, only sons.
The war is for a weak claim, so I might be able to murder my way out of it. Wait, I am a 6 year old. I cannot murder anyone. Another of my kings-with horrible-life-expectancy got invaded by Scotland and England at the same time. England was pushing my aunt's claim on Wales and I couldn't kill her to end the war. Scotland was pushing a de-jure claim on a county. Somehow this all ended up with Wales being Gavelkind and Ireland being Primogeniture.
Of course, when I took the county back from Scotland (because the Duchy is still my vassal), they marched their 8K army into my 9K army at Ulster and got beaten soundly. Then I forgot that attackers can only get 75% war-score from battles and chased their army around instead of speed siegeing the war target. Then my 4000 man army thrashed their 5000 man army a couple times, so GO ARCHERS!
Speaking of, how do the various special buildings add up? Is it per unit? Or per county? Or per character? If I hire an archer heavy mercenary company, do they get the benefit of my Longbow Ground 4?
If they drop stacks in the 1 - 5K range, I can defeat them in short order. What I am worried about is a 10K doomstack. I know that a couple generations ago the HRE had a fleet of 180 ships floating around which dropped a 16K stack on some of my rebels. I am mostly waiting to hire mercenaries until when I actually need them. If HRE gets another war on their radar, I might be able to just let the "Someone controls the war target" thing tick up until I have 100% and can force a surrender.