>I do not have a brother and my maternal grand-father
>and his only brother are deceased. How can I trace
>that side of the family? Also, can someone give a
>DNA testing center other than African Ancestry?

Look at your cousins. On your mother's side, does she have a brother, with the same father? If yes, is he living and if not, did HE have a son?? Did your maternal grandfather's brother have a son? Grandson thru a son? Any of those would be the lineage of your maternal grandfather.

As an example, both of my parents and all of their siblings are deceased.

I tested myself to get my maternal grandmother's lineage.

I am testing my mother's brother's son's son to get my maternal grandfather's lineage.

I am testing my father's sister's daughter's daughter to get my paternal grandmother's lineage.

I am testing my father's brother's son to get my paternal grandfather's lineage.

And don't forget, even if you had a brother he would not carry your maternal grandfather's Y-chromosome. His would be your father's (and paternal grandfather's) Y-chromosome.

As to another testing center, it depends on the results you are looking for. As far as I know, African Ancestry is the only one matching to specific African population groups.