As a comment, this image is missing one potential relationship.
I.E. A parent that is an identical twin. Thus, first cousins born from the twin are genetically also "half-siblings" rather than cousins. While it's not very common, it does happen.
Talk pages are where people discuss how to make content on Wikipedia the best that it can be. You can use this page to start a discussion with others about how to improve the "File:CousinTree kinship.svg" page.
