Ran into a roadblock, got hit by England backing a dude laying claim on Brittany, and not only was my armies severely outmatched (even with mercs hired) to begin with, my 20-25 something martial king decided to beat it in a fight, leaving me with an underage heir and a bunch of rebellious Irishmen (especially the damned Duke of Ulster, he's taken both half of Connacht as well as Dublin besides his own duchy, though at least I'm still hanging on to Ulster County itself) all wanting the crown of Ireland for themselves. Then the "just" king of Scotland decided to make an attack of opportunity while I was down and pressed the claim that one of his courtiers had on Connacht. I guess I was lucky Duke Ulster owned half of it, after all, since I only lost one county to them.
Though this might yet turn out in my favour. Since neither Brittany or Connacht was in the de jure realms of England or Scotland, the they ended up as sovereign states after the war, and I still have claims on both of them. Brittany has some duke level allies, so he might be trouble, but the new duke of Connacht has no allies of mention at all, just a couple of counts and barons, so I'll have no trouble getting that back - plus there's now another independent state in Scotland I can lay eventually lay claim to. And the best part is, since my heir is still underage, I have his whole life in front of me to do it. Just need to rest and regroup a little first, and hope the Duke of Ulster doesn't cause any more trouble.