There was a beautiful village called Xielixiang, where thirty to fifty households lived side by side in two neat rows of south-facing houses. In front of the homes lay a large threshing ground, and to the south stretched a long line of earthen mounds covered with tall trees, with distant green mountains faintly visible beyond. At the eastern edge of the village, a pond served the villagers for washing rice and vegetables.
In Xie Li Lane, two brothers named Xie each had a son on the same day. At the full-moon banquet, they invited all their relatives and neighbors to celebrate.
During a family gathering, the two brothers each brought out their newborn sons, both wrapped in identical swaddling clothes and cloaks.
The guests eagerly held them in their arms, praising in unison, "Look at these two children, both born with full foreheads and bright eyes—they will surely achieve great things in the future!"
The Xie brothers were grinning from ear to ear, unable to contain their joy.
By the time they were three or four, in spring and autumn, the children would play together in the shade of a mound; in summer, they'd share a tub in the pond to gather water chestnuts. They were equally playful, equally well-behaved.
The eldest son insisted on sending his child to a private school at age six or seven, while the younger son disagreed and let his child play freely. The younger son's wife secretly mocked her brother-in-law as a "fool."
The eldest son’s child, now twelve or thirteen, studied diligently and made great progress, while the younger brother’s child followed his father learning to farm. No longer playing together, the two cousins gradually grew apart.
The two children had reached twenty years of age. While both were blessed with pleasant features, one was refined and elegant, while the other was utterly unreasonable.
The great Tang Dynasty scholar Han Yu once told his son Han Fu, who was studying at his Chengnan villa, a story about two children: "At thirty, one becomes a dragon, the other a pig... One ends up as a common soldier, his back scarred from whippings. The other becomes a noble's advisor, living in grand halls." Han Yu used this tale of "One Dragon, One Pig" to warn his son that only through relentless, tireless study could one achieve greatness. Today, this idiom describes two people from the same background who end up worlds apart in wisdom and achievement.
Source: Han Yu (Tang Dynasty), "Poem on Reading in Chengnan"
Meaning of the Idiom: Later, the Chinese idiom "一龙一猪" came to describe how two people from the same background who end up worlds apart in wisdom and achievement.