How native do you have to be to enroll in a tribe?
Every tribe has their own requirements for enrollment. Some tribes base this off of blood quantum (how much tribal blood you have), while others base it off of lineage, or a combination of both.
I tried looking on Tohono O’odham’s official website, but it was must be down (www.tonation-nsn.gov). However, I did find a number you can call – 520.383.8700.
If your grandfather was an enrolled member of the tribe, they should have a record of it. If they are not finding it, ask your family members if there were any other names he may have used or perhaps even a different birthdate. Sometimes tribal names can be incorrectly recorded for a lot of different reasons (e.g. adoption, the recorder not being able to spell tribal names, families not having a last name, families being given Spanish or English names, etc.).
If you’re having trouble, call the enrollment office and just let them know that you need help. They may give you some suggestions for doing your own research by checking out a database they use, or going to the local library, museum, or State University. Ask them what they suggest you do.
If you’re still not getting anywhere, see if you can talk to someone else. Sometimes it’s a matter of finding the right person to talk to.
Best of luck!