"On November 22, 1998, Grandmaster William Cheung was inducted into the 1998 Blitz Hall of Fame. He has been called 'The Masters' Master' and was considered by Bruce Lee to be the 'ultimate fighter'. William Cheuk Hing Cheung was the sole inheritor of the Traditional Wing Chun Kung Fu system, and was the person responsible for introducing Bruce Lee to Wing Chun Kung Fu.

In 1951, at the age of ten, Cheung started his training in Wing Chun Kung Fu under the late Grandmaster Yip Man. From 1954 to 1958 Cheung was a live-in student of Grandmaster Yip Man. It was during this time that he inherited the complete system of Traditional Wing Chun Kung Fu."

Bio from the official William Chueng website.

Lineage 1: Yip Man -> William Cheung
Lineage 2: Unknown -> William Cheung (possibly Garrett Gee, or another Hung-Fa Yee Lineage master).