Like any of this is new? The arisotcracy has a long history of recognized bastardry running back to Roman days. The word "fitz" means "illegitimate issue". And anyone named "Fitzroy" was originally descended from illegitimate children of kings/royalty (roi). King James I had literally dozens of illegitmate children but no legitmate issue, which lead to one of England's many wars of succession. Many aristocratic families were founded by bastard blue bloods who were given minor titles and land to keep them from competing with their legitimate half-siblings. Some even became trusted royal ambassadors or were married into royal and/or wealthy families. And since these men are married off to secure family holdings, rarely out of love or physical attraction, it's fairly wise to assume that every royal male has a least one illegitmate child in the woodpile, if not more--and that they might genuinely favor their love-child (in terms of affection and attention) over their legal issue.
*There is also a surname prefix that designates someone is the illegitmate issue of a cleric (such as bishop/cardinal/pope), but I can't remember what it is.