Need help uniting Ireland. (Vanilla + Ruler Designer )

So started Irish because that’s what noobs do. I have taken all of southern Ireland. Now though the rest has no claimants on any duchy or county. No children that I can marry with. Fabricate claims is not working. The Pope who likes me will not let me invade. Tried to sow dissent but my guy was jailed. I am at a loss. What do I do?