Would my mother's paternal aunts become her sisters due to the definitive suckling between my mother and her paternal uncle from my grandmother and my mother's grandmother?

If your grandmother is your mother's mother, and your uncles were not suckled by either of your grandmothers, then they are not your mother's siblings. However, if your grandmother is your father's mother, we request clarification because the ruling differs. In that case, your mother might become the suckling daughter of her husband's father, rendering her marriage invalid, but your mother's uncles would not become her siblings. Note that all of your mother's uncles are mahram to her, even if they are not her suckling siblings.