Heir problems?

The solution.

Build up a connected fleet to some far away island e.g. Ireland, Malta etc

Send the appropriate "Gay, Mental" heir to the Island as a errr....Recon force...*Ahem yes recon*

Remove the fleet surrounding the Island so the heir is cut off from retreat.

Heir is tragically killed or rots in a dungeon for the rest of his pitiful life.

Everyones happy