Galilee

Rich and powerful, the Geary dynasty has reigned over American society for decades. But it is a family with dark, terrible secrets. Its adversaries are the Barbarossas, a clan whose timeless origins lie in myth. When Galilee, prodigal prince of the Barbarossa clan, meets Rachel, young bride of the Gearys' own scion Mitchell, they fall in love, consumed by a passion that unleashes long-simmering hatreds. Old insanities arise, old adulteries are uncovered, and a seemingly invincible family will begin to wither, exposing its unholy roots.

Synopsis from Open Library.