Convergent evolution happens all the time but taxonomy is nonetheless based on ancestry.

Also "horizontal gene transfer" happens in bacteria, and even happens in multicellular sexually-reproducing organisms after viral infection in some cases. Taxonomy should be a directed acyclic graph, not a tree.

For a fun somewhat related topic, it was neat to see the hierarchy of strings and characters in Common Lisp the other day. Can be used to illustrate a bit of the shortcoming of using ancestry to answer if two things are related. https://lispcookbook.github.io/cl-cookbook/strings.html#stri...