The term “grandnephew” usually refers to your nephew’s son. He is a blood relative to you as long as he is your sibling’s offspring because you share the same lineage.
Therefore, your grandnephew is also the great-grandson of your parents and your sibling. The child is your half-great-nephew if he is the offspring of a half-nephew of yours. Although the phrases “grandnephew” and “great-nephew” are frequently used interchangeably, they both denote the same thing. There is no change in the real definition; the only variation is in the particular geographic areas or cultural groups that use the phrase.
