In the Season 3 episode "Felix", Felix asked to be told the Graham de Vanily story about the Twin rings again and Amelie said that Felix was always asking her to tell him the story. So if Felix was always told the story (which I think was acted out by him and Kagami in "Representation") does this mean Felix has known him and Adrien were Sentimonsters since the very beginning?
If you wanna be pinged in my theories let me know!