The achievement is dumb, as well, as other achievements based on luck. I know they wanted to refresh achievements because we're somewhat tired of Conquer Iberian peninsula with nation_01 but still.
there are what 2 "based on luck" including this 1, maybe 3.
The Princess is in this castle
Electable!
Die Please Die
Except they aren't really, there are OPM strats for Electable! or you could just be Austria force your PU over Bohemia after making them as small as possible and then inherit them
Die Please Die, has multiple possible starts, I would advise Timurids but others can be attempted, just dont make your ruler a general and cross your fingers, this is probably the most luck based
On current patch, go into your Women in History event files find a nation that will get a female heir event after the date you can get a royal palace, achievement done, with the change, its also easier since you just have to build a Castle in your capital and wait for a female heir or a Women in History event and its much more time since you can keep an eye out for a princess asap instead of hundreds of years in