Your grandfather's brother's grandson is your great uncle's grandson.
The grandchildren of great aunts and great uncles are your second cousins.
brother
My Cousin Brother
Two people whose grandfathers were brothers are second cousins to each other.
what is my mater name
Your grandson.
He is your grandson. If his father is your son, he is your grandson.
Second cousins.
할아버지 (Hara buhjee)
What is your great-great-great grand nephew?!
He would be your great-great uncle.
Your father's grandfather is your great grandfather.
Your grandfather's brother is your great uncle.
He would be your great great uncle, but you could call him whatever endearing name you both prefer. my great grandfathers brother or my great uncle
grandson....