If your grandmother was Yaqui, or your great-grandmother, or someone the family stopped naming: you belong, cousin. You don't have to look the part, speak the language, or carry the ceremonies to be who you are. You are indigenous whether you practice the traditions or not. The thread was cut a long way upstream from you, and none of that is your fault.
I know the bind: claim it and someone calls it appropriation, stay quiet and you keep the hole where your identity should be. Reaching for what already runs in your blood is not theft. Recovery is not appropriation. You come to learn, slowly and with respect, not to crown yourself anything.