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How did the Roman meaning of consanguinity connect common ancestry with inheritance?

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consanguinity (Left) Absence of inbreeding: horizontal lines connect mates, vertical lines connect parents with their child; (right) an inbreeding loop: horizontal bar at top of loop connects brother and sister, all other lines and bars as above

In Roman society, the concept of consanguinity—derived from the Latin consanguineus or "of common blood"—was fundamentally linked to the structure of the family and the transmission of property.12

The term originally implied that individuals shared the same father, which established their status as members of the same household under the authority of the paterfamilias. Because the paterfamilias held title to all family property, this shared ancestry defined the right to participate in his inheritance.13

In the context of intestate succession, this connection evolved over time:
* Early Law: Succession was primarily restricted to those under the paterfamilias's power (sui heredes) or, failing them, the nearest agnatic relatives (those related through the male line).43
* Justinian’s Reforms: By the time of Justinian, the legal system shifted to prioritize blood relations, organizing heirs into classes based on their degree of consanguinity to ensure that family wealth remained within the bloodline.3

Ultimately, the Roman understanding of consanguinity served as a legal mechanism to define who was entitled to succeed to the rights and duties of a deceased relative.14