Bro. Paul Sun was born in Chek Feng in the Northern Province of Jehol. He was a member of a Chinese Congregation of Teaching Brothers, called the Brothers Disciples of the Sacred Heart, founded by the Scheut Bishop Jensen. He took up teaching as his life's mission and founded quite a number of primary schools, after graduating from Fu-Jen Catholic University. In 1940 he was elected Superior General of his congregation, which had at that time about 45 Brothers. In 1949 he left for the missions in Indonesia and founded a very famous secondary school there. Later he came to Hong Kong and taught at La Salle College . In 1971 he was made an Affiliated Member of the De La Salle Brothers.

In 1958 Bro. Paul Sun founded the St Joseph's Anglo-Chinese School in Ngau Chi Wan. This school, built on faith and love, was named after his great Patron - St Joseph. Bro. Paul Sun founded a large school, one of the biggest private schools, providing over 3000 school places offering excellent education. He guided the destiny of his school with his head as well as with his heart. He never advertised his school. He worked quietly and modestly to make his school earn a good name. He had long decided to rebuild the primary school to give pupils better opportunities for a fuller education.

But Bro. Paul Sun peacefully passed away on 13 March 1986, before the new primary school building was completed in 1987. Fittingly, he died in the month of St Joseph, and close to the feast of his great Patron. He was indeed a completely dedicated man of God, a true gentleman, an outstanding educator, and many say, a saint.