Well, it depends on what you want to say.
parentDirectoryPaths:
There is a parentDirectory and it has multiple Paths. Does not make any sence.
parentDirectoriesPath:
Many parentDirectories with the same Path (does not make any sence).
parentDirectoriesPaths:
Many parentDirectories with their Paths. Maybe a List of Tupels.
So if you have one parentDirectory it would be parentDirectoryPath.
And if you have many (plural) of them it would be parentDirectoriesPaths
Since only you last example made sence, I'm guessing it is your solution.