To be consanguineous is to be related by blood. A mother and her biological child are consanguineous.
Consanguineous comes from a Latin word meaning "of the same blood," and that's exactly what this word means. This word applies to everyone who is a blood relation: a mother and father are not consanguineous, but they are both consanguineous with their biological children. All the puppies or kittens in a litter are consanguineous. First cousins are consanguineous. An adopted child will not be consanguineous with anyone in his or her adoptive family.