first cousin

plural first cousins

1. A child of a parent's sibling; a nephew or niece of a parent; a child of one's uncle or aunt.
2. A relative who has with the other person only two grandparents or one grandparent (maternal or paternal) in common, but parents are different.
3. broadlyfigurativelyAnything closely related.

   […] that coarseness which is first cousin to sin.

   1878, Connecticut Churchman, volume 37, page 246

   1 more example

   [H]e was afraid the Mexicans, who were, he claimed, first cousin to the spigotties, would catch us off our guard and give us the same treatment.

   1920, Boys' Life, volume 10, number 4, page 22