Symmetry promotes systemic stability. When Henry IV overthrew Richard II in 1399, the Wars of the Roses, involving issues between the House of York and the House of Lancaster, concerning succession to the British throone, were the result. In 1485, when Henry VII of the House of Lancaster married Elizabeth of the Hourse of York, the pattern of succession once again became clear. Generally speaking, a graph is a collection of nodes together with edges linking pairs of nodes. There may be more than one component to a graph.
Some graphs are trees.
The subject of graph theory is a very broad one with numerous applications. The classical text in graph theory is by Frank Harary, entitled Graph Theory, published in 1969. A partial genealogical table of the famiily relationships, for both the Houses of Lancaster an York, is shown below. This genealogical table can be made into a digraph. Let each person represent a node.