Isn't this what we'd expect?

From the Telegraph

When the body of Richard III was discovered in a car park in Leicester in 2012 archaeologists knew it was a momentous find.

But little did they realise that it might expose the skeletons in the cupboard of the British aristocracy, and even call into question the bloodline of the Royal family.

In order to prove that the skeleton really was Richard III, scientists needed to take a DNA sample and match it to his descendants.

Genetic testing through his maternal DNA proved conclusively that the body was the King. However, when they checked the male line they discovered something odd. The DNA did not match showing that at some point in history an adulterous affair had broken the paternal chain.

Queen that had a bloke on the side, gay/impotent king who got his wife to shag another bloke to get an heir. In 700 years, I'd expect it to happen a few times.