your great grandfather’s death certificate likely shows his parents names. you can look at it for free at your town hall. it might even say MAYO as birth place.
I ran into an acquaintance at church yesterday ... it occurred to me that she might be related to my cousins .... after 3 minutes we realized that we were cousins. She is my mother’s 4th cousin. I never would have known without researching because how would I know her mother’s maiden name?
Thanks for the information - I will look into it !