Brother Mark.
You are right. Brother Stephen is in his 90's and still teaches in various conferences. In many of his teachings he shares about his relationship with Brother Watchman Nee.
Short Biography:
"Stephen Kaung, a Christian teacher originally from Mainland China, was the son of a well-known Methodist minister. He became a Christian at an early age and was at first active in the Methodist Church. In the early 1930's, he met Watchman Nee for the first time and he later became his co-worker in China. He worked with Nee in China until 1949 when he left the country and became involved with Christian work in other areas of the Far East. In 1952, Kaung moved to New York City to join a "Little Flock" assembly which included immigrants as well as missionaries returned from China. In 1957, following trouble within the group, Kaung moved to San Francisco to join another church there. The following year, he moved back to New York after travelling to Europe with Witness Lee. In 1971, he moved to Washington D.C., but periodically travelled back to the New York group to speak and hold conferences. However, in 1973, Kaung stopped associating with the Local Church and continued with his own ministry. Throughout the 1960's, Kaung worked closely with T. Austin-Sparks
Stephen Kaung's major work has been to translate the writings of Watchman Nee into English, over 50 titles, which have been published by Christian Fellowship Publishers (CFP) in Richmond, Virginia, where Kaung continues to minister today.
Stephen Kaung currently resides in Richmond."