In Kotlin, we can get the sister directory path using the resolveSibling method provided by the java.io.File class.
Here's an example:
val currentDir = File(".")
val parentDir = currentDir.parentFile
val sisterDir = parentDir.resolveSibling("sisterDir")
In the example above, we're first getting a reference to the current directory using the . notation and creating a File object. We then obtain the parent directory using the parentFile property of the File object. Finally, we call the resolveSibling method on the parent directory and pass the name of the sister directory as an argument to obtain its path.
Note that the sister directory should be located in the same parent directory as the current directory for the above code to work.