Consanguinity, literally meaning common blood, describes a family relationship between two individuals. A consanguinity chart (or table), as seen below, is often used to illustrate that relationship.

In the Catholic Church, a marriage with a direct line relative or collateral relative to the fourth degree is grounds for an annulment. In other words, you could not marry your 1st cousin (4th degree), grand nephew/niece (4th degree), but you could marry your 1st cousin once removed (5th degree).

Given that most of the nobility of Europe were and still are in-bred to one degree or another, consanguinuity was often used by European nobility as a convienient means of divorce, espoecially in ages when religious doctrine forbade the voluntary dissolution of a failed marriage.

The succession law known as consanguinity, requires that the next monarch be of the same blood of the previous monarch; allowing, for example, illegitimate children to inherit.

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