Great or Grand

[Gadget]

Best wishes, Guy.

you say:

n other words the term Aunt or Uncle replaces the term Grand.

We're talking about the next stage.  Aunt and uncle are the siblings of one's parents in our bifurcate merging system of kinship terms.  Grand A and U  are the siblings of our grand parents.

[Gadget]

I don't have my Anthopology Kinship text books to hand but  ...

Kinship Terminologies

Kinship is one of these more complex systems of culture. All human groups have a kinship terminology, a set of terms used to refer to kin. Many parts of life are impacted by kinship, and in most societies kinship relations influence things like who one can and can not marry, who one must show respect to, who one can joke with, and who one can count on in a crisis.

Kinship terminologies vary in different societies from as few as twelve to more than fifty terms. English kinship terminology is in the middle, and contains the following principal terms:

mother, father, son, daughter, brother, sister
uncle, aunt, nephew, niece
cousin (differently elaborated in different English speaking cultures)
grandfather, grandmother, grandson, granddaughter
granduncle, grandaunt, grandniece, grandnephew (in many dialects)
plus
great-grandmother, great-great-grandmother etc.
and
great-grandfather, great-great-grandfather etc.

http://era.anthropology.ac.uk/Kinship/kinIntro.html