I created a simplified version the royal family tree which only shows the blood ties between monarchs and three critical intra-marriages.

With a line:

The least related successive monarchs according to consanguinity were:

  1. Richard III to Henry VII — third cousin once removed: 0.195% + trace contribution from Ann Mortimer.
  2. Henry VI to Edward IV — third cousins: 0.78%
  3. Queen Anne to King George I — second cousins: 3.125%;
  4. Queen Elizabeth to King James I: double first cousins twice removed: 6.25%
  5. Stephen I of Blois to Henry II — first cousin once removed: 6.25%
  6. Edward VI to Lady Jane Grey — first cousin once removed: 6.25%
  7. Richard II to Henry IV — first cousin: 12.5%
  8. William IV to Victoria — niece: 25%
  9. Edward III to Richard II — nephew: 25%
  10. Edward V to Richard III — uncle: 25%
  11. All others were children and siblings: 50%