The British royal family can trace its ancestry back to the kings of Wessex and Kent, at least 1300 years, though it gets a bit murky beyond that. The family tree on this site links both the English line and the Scottish line through a descendant of Alfred the Great. Often through the female line, and sometimes through collateral lines that have long been separated from the main tree. But still.
Holy Cow. Charles II created a heap of dukedoms for his illegitimate children. It makes some of the Regency snobbery amusing. Those are fantastic charts. Thanks for reminding me to follow the female line. The are descended directly from the VAST majority of the kings and queens, but not Henry VIII through Elizabeth or any Stuarts after James I. Most of the other cases are ones with no heirs like Edward the Confessor. WOW
Being a *royal* mistress was quite different to being the mistress of a mere noble or (heaven help the poor dear) a mere commoner! But even then, when it came to the children, whether or not you were acknowledged by your father was everything.