As nouns the difference between grandnephew and grandson
is that grandnephew is grandson of one's sibling while grandson is a son of one's child.
grandnephew
English
Noun
(
en noun)
Grandson of one's sibling.
# Brother's grandson (fraternal grandnephew'') or sister's grandson (''sororal grandnephew )
# Son of one's nephew or niece.
Synonyms
* grand-nephew
* great-nephew
* greatnephew
See also
* nephew
* niece
* grandniece
* second cousin
* granduncle
* grandaunt
grandson
English
Noun
(
en noun)
A son of one's child.
Synonyms
* grandboy
Antonyms
* (with regard to gender) granddaughter
* (with regard to ancestry) grandmother, grandfather
Hypernyms
* grandchild