The relation kind_von/2 is visualized as a directed graph with some highlighted nodes. Below pairs of sibilings are outlined. 
kind_von(joseph_I, leopold_I).
kind_von(karl_VI, leopold_I).
kind_von(maria_theresia, karl_VI).
kind_von(joseph_II, maria_theresia).
kind_von(joseph_II, franz_I).
kind_von(leopold_II, maria_theresia).
kind_von(leopold_II, franz_I).
kind_von(marie_antoinette, maria_theresia).
kind_von(franz_II, leopold_II).
:- digraph_(kind_von/2,[A,B]) <<< dif(A,B), kind_von(A,E), kind_von(B,E).
@@	%  A = joseph_I, B = karl_VI, E = leopold_I.
@@	? Weitere Lösungen mit SPACE

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