You could merge him away; if you do: Detach him from his father, then merge him with his father.
HOWEVER, if you merge him away, somebody may very likely come along and re-create him again. He exists on at least one other genealogy site (linked to below by Frank), and chances are he exists on other web sites.
Therefore, you might want to keep him; detach him from his father, but create a "Disputed Origins" section for him that links to his purported father but explains why he likely did not exist.
Then when people come along trying to recreate him, they'll see that and hopefully become educated about the problem.