first cousin

noun3

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. •
   (figurative) Anything closely related.

   • […] that coarseness which is first cousin to sin. — 1878