Marx (who to be fair was operating in a very different global economy) explicitly excluded servants and other service labor from the proletariat, because he had an extremely industrial (cough gendered) definition of “productive labour.” That being said, he was friends, intellectual collaborators, and possibly lovers with the housekeeper.

Disclaimer: I am no marx historian; my knowledge of marxist theory tends toward literary analysis. I may be simplifying to the point of wrong.