Bad Blood by Christine Pope

The star-crossed love that started it all...
Hannah McAllister's future is laid out before her, as clear as her journey from Scotland to Arizona, where she will exchange vows with her dull-as-dishwater betrothed, Boyd. But for a precious few hours, she is free to explore the wonders of New York City, where she encounters a handsome, compelling warlock, Nathan Wilcox.
Nathan didn't run into Hannah by accident. His brother and head of the clan, Jeremiah, sent him to learn more about the newest witch family to make an appearance in New York. He feels an instant, soul-deep connection to Hannah, but he, too, is betrothed to another based on clan loyalty, not love.
A walk in Central Park, a kiss, and the die is cast for love, betrayal, and a spell that will reverberate for generations to come...
Warning: Contains a star-crossed relationship that doesn't end in a HEA, but sparks a chain reaction of love that echoes down the generations.