Many French Royals escaped the guillotine. The term Prince du Sang refers to the male relatives not heir-apparent. More specifically Prince of the Blood (a blood relation if you will) Many fled the country to avoid the guillotine. My family are descendants of the Huguenot Exodus at the time of Henri IV and are of Bourbon descent. I am not an expert on the French Revolution but it would stand true that here would probably been some escapees.