Parallel pages in a wiki are distinct pages that should not be distinct, but rather should be merged.
For example, User 1 creates a page called "Toledo" and User 147, not knowing that "Toledo" exists, creates "Toledo, Ohio". Once the parallel pages are created they will sow confusion as they may contain different answers to the same question.
1. Somebody should redirect one page to the other.
2. or copy the content over from the second page, add it to the first, delete the second page and add an alias to the first page.