oldebarn = great grandchild
there isn't a word for granddaughter or grandson - both are refereed to as 'barnebarn' = grandchild (same goes with 'great ...' -but it's "oldebarn")
Barnebarn
The word is "bisnieta". Note that "nieta" alone means "granddaughter".
Mujuku
Your granddaughter is your brother's grand niece (or some would say, great niece).
Your granddaughter is your brother's grand niece (or some would say, great niece).
Great grandfather in Danish is "oldefar."
God film.
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.
Your sister is her great grandaunt.
Your brothers great granddaughter is your great great niece.