Rosalyn,
With only you and your brother as candidates, your brother will be able to test for 2 of your family lines......your father, grandfather, greatgrandfather, etc and your mother, grandmother, greatgrandmother, etc. You can only test for 1....your mother, grandmother, greatgrandmother, etc.

To get information on 4 sets of grandparents, your best choice is a maternal uncle and a paternal uncle. You and your brother as testers are limited on the DNA information that you can acquire.

Linda