Earlier quoted context omitted.
Brooks' ?
This is exactly what I am trying to establish to improve my bumpy English. My best guess is that the correct form is "Brooks's" because (1) "Brooks" is a singular noun ending with an "s" and (2) it is not a classic neither religious name. If you claim it should be "Brooks'" I am ok with this as long as you give me a sensible explanation.
Here's an example of the lack of consensus:
Either is acceptable: https://data.grammarbook.com/blog/apostrophes/apostrophes-wi... https://owl.purdue.edu/owl/general_writing/punctuation/apost...
Chicago vs AP style: https://apvschicago.com/2011/06/apostrophe-s-vs-apostrophe-f...
APA style suggests appending the extra 's': https://blog.apastyle.org/apastyle/2013/06/forming-possessiv...