Consanguinity is the quality of being descended from the same ancestor as another person.
The degree of relative consanguinity can be illustrated with a consanguinity table, in which each level of lineal consanguinity (i.e., generation) appears as a row, and individuals with a collaterally-consanguinious relationship share the same row.
The connotations of degree of consanguinity varies by context (e.g., Canon law, Roman law, et al.). Most cultures define a degree of consanguinity below which sexual interrelationships are regarded as incestuous (the "prohibited degree of kinship"). In the Catholic Church, unwittingly marrying a closely-consanguinious blood relative is grounds for an annulment, but dispensations were granted, actually almost routinely (the Catholic Church's ban on marriage within the fourth degree of relationship (third cousins) lasted from 1550 to 1917; before that, the prohibition was to marriages between as much as seventh degree of kinship).
http://en.wikipedia.org/wiki/Consanguinity
IOW, If your family tree looks more like a pole than a tree, you might me an Arab....