Warning: Major Spoilers Ahead for Stranger Things: The First Shadow
Following Henry Creel's tragic act of killing his family, Dr. Brenner assumed custody and transported him to Hawkins Lab. Subsequently, Creel became subjected to drugs, rendering him entirely under Dr. Brenner's control. In a pivotal moment, it was unveiled that Dr. Brenner had been conducting experiments involving blood transfusions from Henry to pregnant women. The culmination of these experiments yielded a positive outcome, referred to as "002," a revelation made apparent when Dr. Brenner introduced Henry to a pregnant woman involved in the experiments.
Through the use of Henry Creel's blood, Dr. Brenner successfully created all the test subjects in the lab. The Stranger Things Play ends with Henry Creel holding newborn Eleven in his arms, expressing anticipation by saying, "I am excited to see you, 011. I have plans for us."
Eight years later, Henry Creel strategically deceived Eleven into removing his controlling chip. Seizing the moment, he proposed that she join him in forging a new world order. This revelation suggests that Henry Creel had planned it all along and was awaiting Eleven to grow up before pitching his vision to her.
Eleven was born in 1971 to her mother Terry Ives. Stranger Things: The First Shadow does not provide any information about his father. Many fans have theorized the possibility of Henry Creel being the father of Eleven. However, the play clarifies that Terry Ives was already pregnant before Dr. Brenner conducted blood transformations with Henry.
Though all the test subjects can be called siblings because they all share the same blood. That is why the season 2 episode 7 that introduced Kali aka 008 was called "The Lost Sister".
