This example shows a family tree as a hierarchical node-link diagram, with color-coded circles representing generations: red for the grandparent, orange for the parent level, and green for descendants. Using D3 v7, the code applies `d3.stratify` to convert the flat array of family relationships into a tree structure, then lays it out with `d3.tree` and renders vertical links via `d3.linkVertical`. Nodes are drawn as SVG circles with text labels above them.