In the final years of the Qin Dynasty, after Xiang Yu and Liu Bang's armies had toppled the Qin, they turned against each other in a bitter struggle for supremacy—the famous Han-Chu conflict.
Xiang Yu first set up the "Hongmen Banquet" at Xinfeng Hongmen (east of present-day Lintong County, Shaanxi), but unfortunately failed to kill Liu Bang.
Soon after, Xiang Yu led his troops into the Qin capital Xianyang, executed the surrendered Qin emperor Ziying, declared himself the Hegemon-King of Western Chu, and enfeoffed Liu Bang as the King of Han.
In the spring of the second year of the Han Dynasty, after quelling the surrendered Qin generals Zhang Han, Sima Xin, and Dong Yi, Liu Bang led 560,000 troops to attack Xiang Yu but was soundly defeated, with his father and wife (Empress Lü) captured by the Chu army. Trapped in Xingyang city by Xiang Yu's forces and facing imminent danger, Liu Bang had to flee with a small group of men. Afterward, he took command of the army he received from Han Xin and continued his standoff against Xiang Yu.
Xiang Yu, frustrated by Peng Yue's forces disrupting his supply lines and unable to quickly defeat Liu Bang, set up a tall chopping block in his camp. He pressed Liu Bang's father onto it and declared, "If you don't retreat today, I'll boil and eat your father!"
Liu Bang replied, "You and I, Xiang Yu, once both supported King Huai of Chu and swore brotherhood, so my father is also your father. If you truly intend to boil and eat my father, then share a cup of broth with me!"
Xiang Yu was furious at Liu Bang's words and truly wanted to kill Liu Bang's father on the spot. But his uncle Xiang Bo advised him, "It's still unclear who will ultimately rule the empire, and those contending for it never care about personal family ties. Killing Liu Bang's father now would only deepen his hatred and bring you no benefit."
After some thought, Xiang Yu found the reasoning sound and abandoned his plan to kill Liu Bang's father.
Later, the idiom "Share My Cup of Soup" came to describe sharing benefits.
Source: *Records of the Grand Historian*, "Biography of Xiang Yu"
Meaning of the Idiom: Later, the Chinese idiom "分我杯羹" came to describe sharing benefits.