um Nung (Cen Neng) was born in Peru in 1926 but was brought to Foshan, China as an infant by relatives so that the family name would continue in its land of origin. When the Japanese invaded, however, Sum's family lost contact with their relatives in Peru and over night went from a life of prosperity to one of poverty. Determined to help support his family, Sum took a job at Tien Hoi restaurant. Sum Nung was often forced to defend himself from local bullies, and this eventually, in 1938, led him to seek wing chun instruction from fellow staff member, Cheung Bo. The chef, seeing a great deal of determination in the child, agreed to take him as a student.

Yuen Kay-San would often drop by Tien Hoi to visit his friend Cheung Bo and take tea. After dining at the restaurant, he would sometimes remain behind and watch the staff practice their wing chun. While observing, he would stay quiet and would never comment nor criticize. Over time, however, he grew to admire the dedication of Sum Nung. In 1940, Cheung, respecting the tremendous quality of Yuen's wing chun, and knowing that he had already taught the youth all he could, introduced Sum Nung to Yuen. Sum Nung was hesitant at first. He had been learning from Cheung for a few years and saw Yuen, older and quite slender, as a stark contrast to his young and powerful teacher. This feeling led him to question Yuen's skills. Yuen, seeing in Sum Nung a great desire and potential, was willing to indulge the youth. Promising that the youth could use all that he knew, and vowing only to defend in return, Yuen invited Sum Nung to touch hands with him. Quickly realizing that Yuen's skills were of the highest level, Sum Nung immediately became his student.

From Yuen Kay-San, Sum Nung learned the fists, the dummies, the pole, the knives, and worked at developing his sticking hands and fighting skills. When not practicing, Sum would sit beside Yuen Kay-San while Yuen discussed wing chun's concepts. Under Yuen's guidance, Sum continued to refine and polish his wing chun, developing an intelligent and practical style, as simple and efficient as it was well rounded and effective.

By the 1943, Sum Nung had gained a great reputation for his wing chun fighting skills in Foshan and had begun to teach students of his own. In the late 1940s, when Sum Nung was just over 20 years of age, he decided to move to the nearby provincial capitol of Guangzhou to pursue his medical career. In the early days, he supported himself by teaching wing chun and providing medical services to members of the Iron Workers Union, Restaurant Workers Union, Five Metals Union, and other guilds.

Although Sum Nung, like Yuen Kay-San, did not boast of his abilities nor seek out confrontation, he did on occasion have friendly tests of skill with practitioners of other martial art styles. Although he seldom spoke of the encounters out of respect for his opponents' reputations, it is said that in them, he never met with failure and his reputation in Guangzhou grew steadily. Following the formation of the People's Republic of China, Yuen's health had begun to deteriorate. Yuen passed away from illness in November 1956.

When Sum Nung returned to Guangzhou he began working in a local clinic. He continued to teach wing chun kuen, but due to the politics that followed the Communist rise to power and the subsequent Cultural Revolution, he did so privately, not wanting to attract too much attention. Over the years, teaching only those whom he felt were upright and trustworthy, grandmaster Sum Nung went on to train many outstanding students.

Among Sum Nung's earliest students was his own uncle, Sum Jee. Other students from the late 1940s to early 1960s included former dragon shape boxer Lao Lo-Wai (known as "Mang Wai"), former Ngok family boxer, Ngok Jin-Fun, Pan Chao, and Leung Dai-Chiu (who moved to Hong Kong around 1970 and later to the United States). From the mid-1960s, his students included Dong Chuen-Kam (deceased), Ngo Lui-Kay (Ao Leiqi, who relocated to Canada in 1982), Fu family internal stylist and Wrestling champion Kwok Wan-Ping (who established the Guangzhou Wing Chun & Tai Gik (Taiji) school in Hong Kong in the late 1960s), and Lee Chi-Yiu (who moved to Hong Kong in the early 1970s). Around 1980, Sum Nung also taught opera performer Siu Siu Gai. Others over the years, such as Wong Wah (Tom Wong) who relocated to Los Angeles helped introduce the style to the United States, as did Dr. Wong Tiet-Wai (Teddy Wong) in New York City.

Also in the Los Angeles area is Chu Sau-Lei (Robert Chu), student of Kwan Jong-Yuen who's lineage descends from Ngok Jin-Fen and Pan Chao. Several of Kwok Wan-Ping's early students also brought the art to North America, including Dr. Tse Chung-Fai in British Columbia, Chow Gwok-Tai in Ontario, and Lee Chung-Ming in Virginia. Lo Kuen-Hung (Henry Lo), who learned the art from Leung Dai-Chiu and Lee Chi-Yiu, also helped establish it in Ontario. In Australia, students of Dr. Sum Nung such as Cheng Hung-Chuen (Oliver Cheng), have helped spread the art in the southern hemisphere.

Sum Nung has also endeavored to help keep wing chun "in the family", sharing his insights with Yuen Kay-San's grandson, Yuen Jo-Tong and in keeping with a pledge he made his first teacher, Cheung Bo's son, Cheung Ah-Chut as well. In addition, Sum Nung is passing along the art to his own children, including his son, Sum Dek, who assists with teaching.

Grandmaster Sum Nung has continued to develop and refine his art over the decades, concentrating on practical application. This has led to his system being recognized as one of the most effective in China. Today, due to the hard work and determination of grandmaster Sum Nung and of his students and descendants, the art of Yuen Kay-San can be found in China, Hong Kong, South East Asia, Australia, South America, and continues to spread internationally.