I updated Category: Earl Marischal with the correct numbering with a JSTOR citation for Innes' 1927 article, and ODNB links for most of the Earls. The numbering is off becuase the 1st Earl's father is cited by most peerage sources before 1927 as being the 1st Earl, but Innes' research indicates he was probably the 1st Lord Keith, and his 2nd son William was the 1st Earl Marischal.
Because the numbering is wrong in every profile who is linked to one of these Earls, this is a huge lift to change. It is also wrong in Wikipedia, while I corrected the main page, it is a lot of work to move the existing articles to new numbers and correct the text in various linked articles (way worse than Wikitree!).
If you are inclined, I would suggest fixing wikipedia first. Otherwise, I was hoping a Scottish Clan or EuroAristo members would consider fixing all the wikitree profiles. They had a lot of children and it will be wrong all over the place.
If you have JSTOR access, here's the Innes article -> https://www.jstor.org/stable/25525738
On sources, The Complete Peerage 2nd edition has the correct numbering (starting on p.475, before that it has more info on his ancestry), although it is unclear who was the 1st Lord Keith. Cracroft has a good summary and because it is based on BP2003, thepeerage also has the right numbering The ODNB has the right numbering for Earl 1-6, but the wrong numbering for 7-9 (they have 8-10, plus that was how I found Innes article in the first place cited in the 3rd Earl's article!). Note: The Complete Peerage 1st Edition has the wrong numbering, along with the Scots Peerage which also has a summary of the Keith family.