Does the maternal aunt's husband become a paternal uncle or a maternal uncle to the questioner, knowing that the questioner's paternal uncle and his maternal aunt's husband were both nursed by the questioner's grandmother, who did not nurse the questioner's father, and is the maternal aunt's husband unlawful to the questioner?

If the grandmother is common to both your father and your uncle, then your maternal aunt's husband, who nursed from her, would be either your father's paternal uncle (amm) or his maternal uncle (khal). In both cases, he is one of your mahrams, and it is unlawful for you to marry him. However, if the grandmother is specific to your uncle and not your father, then your maternal aunt's husband is not your mahram unless another reason for mahramiya is established. It is a condition for breastfeeding to establish mahramiya that there be five full, satisfying sucklings.