Having Jewish blood on your mother's father's side of the family means that you have Jewish ancestry on your paternal grandfather's side. In Jewish tradition, a person's Jewish identity is typically passed down through the mother. This is known as matrilineal descent, which means that if your mother is Jewish, you are considered Jewish regardless of your father's background.
However, it's important to note that Jewish identity can be complex and is not solely determined by ancestry. Different Jewish communities and denominations may have varying criteria for defining Jewish identity. Some may recognize individuals as Jewish if they have one Jewish parent (patrilineal descent) or have undergone a formal conversion to Judaism.
If you are interested in learning more about your Jewish heritage or exploring Jewish identity, you may want to engage with Jewish communities, study Jewish history and culture, or consult with a knowledgeable rabbi or Jewish organization. They can provide more information and guidance on matters related to Jewish identity and ancestry.