This example displays a family tree as a hierarchical node-link diagram, with circles representing individuals and curved paths showing parent-child relationships. The color of each node indicates its generation depth, using red, blue, and green for successive levels. The code builds the structure from an array of parent-child pairs via `d3.stratify()`, then lays it out with `d3.tree()` and renders the result as SVG circles, paths, and text labels.