https://www.google.com/books/edition/The_Scots_Peerage/LUpmAAAAMAAJ...
Is there more sources, newer that I havent seen because the ones that I do see, say he died with out issue. The way I am reading it, is this Alexander was the brother of Walter and Arthur, illigitimate sons of Walter Stewart who in 1472, these brothers all received legitimation letters.
Walter the brother of this Alexander had a son, Alexander that inherited the title. He became Alexander the 2nd. So it appears that an extra generation here is added.
Again, I do not know if there are more sources that I havent seen that verifies things differently.
