C would be the most likely choice. "I" and "he" still know each other today. "He" and "I" have known each other from a point 30 years ago up to now, and since we met 30 years ago, he has not changed.
A could work if "he" is now dead, for example. In other words, I knew him for a period of 30 years, starting with the day we met and ending with the day he died. And du