Your great grandparent would be the immigrant. Their child (your grandparent) would be American born, so they would be 1st generation American. Their child (your parent) would be American born and 2nd generation. So you would be 3rd generation American.
However, if your immigrant great grandparent arrived in America as a adult with children, as many did, then your grandparent might also be an immigrant and you would be the second generation born in America.
You are talking about the seventh generation of descendants, it's kind of looking for a needle in a haystack without a name as there may be dozens or more females in that generation.
Step-great-granddaughter
Your brother's granddaughter is your great niece and you are her great uncle if you are a man, or her great aunt if you are a woman..
Your sister's granddaughter is your great niece and you are her great aunt (if you are a woman) or great uncle (if you are a man).
Your aunt is great great aunt to your son's daughter (your granddaughter). Your granddaughter is your aunt's great great niece.
An American born Japanese is called "Nikei America-jin" However, this question could also be referring to generations: Issei = First Generation Japanese, one who has immigrated to another country Nisei = Second Generation Japanese, the child of a Japanese immigrant Sansei= Third Generation Japanese, the grandchild of a Japanese immigrant Yonsei= Fourth Generation Japanese, the great-grandchild of a Japanese immigrant
You granddaughter is a great great niece of your aunt. Your aunt is your granddaughter's great great aunt.
Example: Great-great-great Granddaughter Katie
Your granddaughter is your sister's great niece. Your sister is your granddaughter's great aunt.
5th cousin was the answer first given. This describes the relationship for four generations descended from the first cousins. Therefore it is incorrect. The following explains. The first cousins children, your grandparent's generation, would be second cousins. The second cousin's children, your parent's generation, would be third cousins. Since you are a great-grandchild and you are referring to the great-grandchild of a 1st cousin, you are both of the same generation, the next generation in the lineage. Therefore you are fourth cousins to each other.
Your sister is her great grandaunt.
Your brothers great granddaughter is your great great niece.
Your sister's daughter is your niece. Your sister's granddaughter is your great niece Your sister's granddaughter's daughter (your sister's great granddaughter) is your great great niece. You are her great great aunt, if you are a woman, or her great great uncle, if you are a man.
You are talking about the seventh generation of descendants, it's kind of looking for a needle in a haystack without a name as there may be dozens or more females in that generation.
Step-great-granddaughter
granddaughter
Your great uncle's granddaughter is your second cousin.