A grandnephew, also commonly known as a great-nephew, is the son of a person's niece or nephew. A person who has a grandnephew is known as a great-aunt or great-uncle.
A grandnephew could have great-aunts and great-uncles on both the maternal and paternal side of his family. An alternative perspective on the grandnephew relationship is that this person is the grandson of a brother or sister. The level of intimacy between a grandnephew and his great-aunt or great-uncle varies by family. In some cases, the relationship is distant. At times, though, extended families are very close and the relationship is more intimate.