What evidence proves that John Shakespeare and Joan Shakespeare are the parents of Richard Shakespeare , the grandfather of the bard? Is this not just an attempt to graft a historical ascent line where historians haven't found one?

What evidence proves that John Shakespeare and Joan Shakespeare are the parents of Richard Shakespeare , the grandfather of the bard? Is this not just an attempt to graft a historical ascent line where historians haven't found one?
We do not know who Richard Shakespeare’s parents were. There had been various Shakesperes in the region since about the 13th C, showing up in the records, but we cannot connect them to Richard (and therefore William, that being of course the point of all this). John and Joan have been suggested as his parents but there is no evidence. I would detach them and lock down his relationships.