This example shows a family tree as a hierarchical node-link diagram, where each person appears as a circular node and relationships are drawn as straight black links. The tree layout is computed with `d3.stratify` and `d3.tree`, positioning generations vertically with distinct fill colors. Nodes and links are rendered as SVG circles and paths, with transitions animating link drawing from the parent outward and text labels fading in per depth. The code uses `transition().duration()` to stagger animations and defines custom colors per generation depth.