Giscard is not from a noble family. Giscard d’Estaing in NOT his family’s true name. His pretentions of aristocratic origins made him the laughing stock of the real nobility, and the average bourgeouisie as well. His father or grandfather purchased the particule (d’) when he purchased the estate of a noble family.
Sounds like the so-called “nobility” in Poland. For the last 200 years of the kingdom, titles were sold left and right to raise money for the crown. There are very few Polish aristocrats by blood, as the Jagiello (who were Lithuanian anyway) had a problem reproducing.