This blog suggests that the failure of Richard’s Y-chromosome to match that of the Dukes of Beaufort doesn’t make him a male line descendant of Edward III through the “illegitimacy” of Richard, Earl of Cambridge.
The issue it fails to address is this:
The inconsistent chromosome has several other, more likely explanations – that Richard III’s Y-chromosome has degraded, or that false paternity in the Beaufort-Somerset line is far more probable because the latter is much longer, as we explained here.
Furthermore, as pp. xii-xvi of Ashdown-Hill’s Cecily Neville explain, citing heraldic evidence, the “forked beard” portrait below, said to be of Richard Duke of York (with Cecily), as taken from Penrith church, is far more likely to be of his father-in-law Ralph Earl of Westmorland (with Joan Beaufort). That the portrait doesn’t resemble Edward III is unsurprising because Westmorland’s most recent known royal ancestor was Ethelred II.
We have no DNA taken from Edward III to compare with Richard’s or the Beaufort family’s. Sorry to repeat ourselves, but if people repeat errors, we must do so.