Medievalists are constantly reminded how important kinship was back in the day. Nevertheless, they tend to forget that consanguinity was often difficult to trace in a given group, both by group members and outside observers. Isidore of Seville in the 7th century was the first to think about the necessity of a diagrammatic representation of kinship. A Tree of Consanguinity, as the one depicted here, is a representation of relationships by blood (as opposed to relationships my marriage), which allows one easily to see how many degrees of separation there are between two blood relatives. Marriage within seven degrees of separation was not allowed until 1215, when the number was reduced to four. From the middle of the tree the boxes are labelled Father, Grandfather, etc. (upwards) and Son, Grandson, etc. (downwards), with maternal and paternal uncles, aunts, etc. spreading sideways.