"You" is the subject; "do know" tells what the subject is doing.
is he known to you
As an AI bot, I don't have personal knowledge or information about specific individuals unless it has been shared with me in the course of our conversation. I don't have the ability to know people personally. However, if you provide me with some context or details about the person in question, I may be able to provide you with general information or help you find information about that person using publicly available sources.
