My grandmother, who came from [X] village, married my grandfather who came from [Y] town.
In the early years of their marriage, before my mother was even born, my grandfather got into a disagreement with the owner of a garage in [Z] village, not far from [X] village, who thought my grandfather was a bit jumped up because he was from [Y] town.
This all happened YEARS before my sister, my cousins and I were even thought of, but to this day, when travelling to [X] village, we refuse to refuel at the garage in [Z] village. We also completely intend passing this ridiculous grudge down to the next generation, even though the original owner is presumably long since dead and we don't even really know what the disagreement was about anyway.
What ridiculous long-standing feuds exist in your family?