The degree sequence of a graph is a list (in decreasing order) of the number of relationships of each person in the graph. In the case of Alice, John, Bob, Mary and Sean, it’s <2,1,1,1,1>. (Alice has two relationships, everyone else has one). Degree sequences are properties of unlabelled graphs; there’s no way to tell who’s the person with the two relationships unless you know the labelling of the graph. Graphs with the same degree sequence share various properties.