I have seen a suggestion that Word graphics enable a build. I don’t want to use any of the online sites even if they are free.
Do that in Draw and paste the resulting drawing into Writer.
In Draw, create rectangles for the persons. You can optionally draw ellipses for marriages with the event date inside (any shape in Draw can have text associated with it; this is called labelling).
You link your shapes (rectangles and ellipses) with connectors, not lines. Connectors have a special property: they glue to “hot” spots of the shapes or their centers. When you move a shape to improve the overall readability of the graph, the connectors remain connected to the shape (this is their primary purpose) and the connecting line/curve gets rerouted to accommodate the new geometry.
In case you find a direct connector would intersect the shape despite all your efforts, don’t hesitate to use two or more connectors. A connector can be connected to another connector and keep its property.
Experiment a bit to choose the best kind of connector for your goal.
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