His CEO's unwanted desire

I am thankful that there is such a tradition in our family, because that's why I recovered my wealth. The attorney also knows this very well because all of his ancestors have served us up to them and her next son. Because Mrs. Diaz's ancestor swore to serve the Chuas for the next generation until their race was exhausted. That's all Papa told me then, and he didn't tell me what happened or why Mrs. Diaz's ancestor made that promise. What did my ancestor do to make all of Mrs. Diaz's clan serve us?