The "sensitive" orderly is revealed to be Victor Creel’s son.
This chapter effectively ends the mystery of Eleven's origins. It establishes that: [S4E7] Chapter Seven: The Massacre At Hawkins Lab
Vecna uses Nancy to reveal his backstory, showing her the Creel House and confirming he has been the puppet master since 1979. Why It Matters The "sensitive" orderly is revealed to be Victor