Of course you are related to the great grandson of your great great grandfathers sister. You have common ancestors in your great great great grandparents.
The two of your are third cousins, once removed.
The sister of your great great great great grandfather is your great great great great great aunt. Her great great grandchild is the fourth cousin of your grandparent and your fourth cousin, twice removed.
The great great grandchildren of your great great grandfather's sister are your fourth cousins.
You and the great grandchild of you great-great uncle are third cousins.
Yes, along with your grandfathers' sisters, if any.
Your child and your sister's child share a common grandparent and are first cousins. Your grandchild and your sister's grandchild share a common great grandparent and are second cousins. There is a generation out of synch, so they would be second cousins once removed.
You and your uncle's great grandchild are first cousin, twice removed.
Your great grandfather's half-sister is your great great aunt, the same as his full-sister is.
The grandchild of your great grandmother's sister is your second cousin, once removed.
Your sister would be her great aunt and she would be your sisters great niece.
Your great great grandmother's sister is your great great aunt. Your and her daughter's common ancestors are your great great great grandparents. The daughter and your great grandmother are first cousins. You and the daughter are first cousins, three times removed.
If the daughter is biologically related to you, it would be your great-grandchild. If your husband had his daughter before he married you (which would make her your step-daughter), it would be your step-great-grandchild.
The grandchildren would be the parents, aunts and uncles, and first cousins once removed, of the great grandchildren.
Your grandmother's sister is your great aunt. Her son's child is her grandchild. You and your great aunt's grandchild are second cousins.
You are great great aunt to your niece's grandchild. Your children and your niece's grandchild are first cousins, twice removed.
Your her great great aunt!