Yes, William Bendix, the American actor known for his roles in film and television, had a grandson named William Bendix Jr. William Bendix Jr. is the son of Bendix's daughter, who has kept a relatively low profile compared to his grandfather's fame.
The possessive form is grandson's.
Your first cousin's grandson son is your grandson's third cousin. Your second cousin's grandson is your grandson's fourth cousin. Etc., etc.
The grandson of your first cousin and your grandson are third cousins to eachother.
Your grandson and your brother's grandson are second cousins to each other.
he is the grandson
Your grandson.
Grandson is wyr.
the: le grandson: petit-fils the grandson: le petit-fils
Your first cousin's grandson is your first cousin twice removed.
'Grandson' = 'barnebarn'
The son of your grandson is your great grandson. You are his great grandmother or great grandfather.
Your father's great grandson could be your grandson, or your great nephew.