Was Banquo from Shakespeare's Macbeth a real person?

According to modern historians, Banquo is a sort of "mythical figure" who probably was not real. Shakespeare used, as is well known, the famous Chronicles written by Raphael Holinshed, published in the sixteenth century. In Holinshed's version, the author relates in three or four lines the story of Macbeth's ascent to the throne and the tale of the "weird sisters" that foretold the future:

The words...of the three weird sisters, would not out of his mind, which as they promised him the kingdom, so likewise did they promise it at the same time unto the posterity of Banquo...

Holinshed goes on to say that Macbeth has Banquo murdered, but that his assassins fail to kill his "son named Fleance." Having fled to Wales, Fleance fathered a son named Walter Steward with the daughter of the Welsh prince. Fleance was subsequently murdered, and Walter Steward then fled to Scotland, where he married into royalty. The new king of England when Shakespeare's version of Macbeth was first performed was James I of the Scottish house of Stuart. James traced his lineage to Banquo and Fleance, and so Shakespeare portrayed Banquo, the supposed father to a line of Scottish (and eventually English) kings, as a noble man who was treacherously murdered by the tyrant Macbeth. Holinshed, on the other hand, claims that Banquo was among Macbeth's "trusty friends" that "promised aid" to the usurper in his plot to murder the king. In any case, Banquo does not seem, according to historians, to have been an actual historical figure. 
http://english.nsms.ox.ac.uk/holinshed/texts.php?text1=1587_1262

http://www.shakespeare-online.com/sources/macbethsources2.html

https://www.bbc.co.uk/bitesize/guides/zvswxnb/revision/1