>I thought you were saying i could take my mother,s
>brother,s son who is my first cousin,s sister,s
>daughter and find out our grma,s parental linage.

Keep in mind that with mtDNA, you must have female to female descent down to the person you are testing.

To try to get your maternal grandfather's mother's line, go back up your mother's family tree and look at your mother's father's siblings.

Did your mother's father have any sisters?

If yes, did any of those sisters have children who are still living, male or female? (your mother's first cousins)

If yes, you can test any of them.

If there were sisters who had children but none living, did any of those sisters have grandchildren THROUGH A DAUGHTER who are still living, male or female?

If yes, then that's who you can test.