If the great grandmother of one person was the great great aunt of another, the two are third cousins to each other.
When two people have the same great grandmother, depending on whether they also have other, closer, relatives in common they could be:siblingsfirst cousinssecond cousins
When one person's great grandmother is the another person's great aunt, the relationship between the two people is that of second cousins, once removed.
Where Joe's great-great grandmother is also Jane's great grandmother, Joe and Jane are Second Cousins, Once Removed. (Joe's parent and Jane are Second Cousins.)
Your grandmother's sister is your daughter's great great aunt. Your daughter is the great great niece of your grandmother's sister.
2nd cousins
Your great grandmother's brother's great grandson is your third cousin.
Your grandmother's sister is your great aunt.
great great grandmother
The relationship is probably to be good to the niece
She would be your great grandmother
Your great grandmother's sister is your great great aunt and you are her great great niece (if you are female) or great great nephew (if you are male).
The first cousin of your great great great grandmother is your first cousin, five times removed.