Jack Carter was the sheriff of Eureka and a former U. S. Marshal. He had two biological daughters - Zoe and Lacey - and two step-children.
His first girlfriend, Angela, died in a car crash. Jack was teaching her how to drive, and therefore felt responsible for her death. The police assumed that he sat behind the wheel, and Jack didn't correct them, so he was charged with reckless endangerment. A few years later, Jack met Abby, his first wife. They ended up divorcing because he was more invested in his job than their marriage.
As soon as he arrived in Eureka, Jack began developing feelings for Allison. However, it took a few years for them to actually get together. In the meantime, Jack briefly dated Callie Curie, and had a more serious relationship with Tess Fontana.