The book also calls them the miracle makers. Especially the women in the family.
The D'Angelo's rarely birth males. If they do, there are usually more girls than boys; three to one ratio. All of the women, young and old, whatever generations they are born, are special. They have the strongest affinity to magic and have the densest mana. Maybe it's because every single one of those women is believed to be the closest relation to the Goddess Feronia.
The fallen kingdom of Vern, albeit small, was very prosperous because of the D'Angelos. The land is rich, teeming with life, and had never experienced drought and famine amidst the constant wars. There weren't life-threatening diseases nor grave illnesses that ravaged their lands. Just prosperity. Even after the magic was sealed, the clan stayed the same and had retained their powers.