25% Cherokee says Father- Mother says 0% ???

I found my birth father when I was 27. I had already been away from my mother’s home for 14 years by then. She kicked me out at 13. He said I was 25% Cherokee because he was 50%. He told me his father married his mother back (100% Cherokee) in 1935, but he didn’t know her last name. Her first name was Helen. She married an Al Zorn of St. Louis, MO. They didn’t stay married very long.