Achievement 'The Princess is in this Castle' not working?

[ForzaA]

Starting with no heir (as Hungary and England both do) disables the achievement, despite how you might interpret the achievement description. I believe you need to start as a country that has a living male heir to be eligible.

This is correct.

The description is how it should be working, but a bug means that "no_female_heir = no" returns FALSE if there is no heir (and hence, makes you ineligible for the achievement), and so only countries that start the game with a male heir qualify.