All US Presidents (save one) are related back to King John of England, who signed the Magna Carta in 1215. Are any of the current crop of US presidential candidates similarly related to King John?

You can assume that virtually every person with British heritage (i.e. many tens of millions of people, not just a handful of US presidential candidates) is descended from almost everyone (i.e. not only King John) who lived in Britain that long ago. Check this out:

According to the link in the description, Barrack Obama is technically related to King John of England, including a number of other presidents is there any truth to this?