I never heard them mention Xavier, did I miss that part?

not by name but they talked about him

Ok I am confused, I thought that he mentioned his dad and mom had died and he was adopted, and SK leeched onto him for revenge?

among the last several episodes will be one where the beginning is David standing near a chalk board in a university auditorium and there is a chalk animation shown on the board, the guy fighting the monster in that animation is Xavier

Oh ok thanks