This example visualizes a family tree as an interactive network graph in SVG, using colored nodes to distinguish grandparents, parents, and children. Force-directed layout via `d3.forceSimulation` with link, charge, and center forces positions the nodes, while links represent familial relationships. Nodes are draggable, and a legend maps roles to colors. The code uses D3 v7, applies drag behavior, and renders labels directly on each node.