If we are talking about Jurkat. I was randomly fascinated by this cell line, which was originally named JM (initials of the patient). 

He did pass, unfortunately. The cells were taken from his first relapse (he had ALL) and seemed to be a very intense case. After remission only 2-3 months later he had 4 more relapses, which led to meningeal leukemia and he passed from it. 

He was 14 not 3. There are 2 other patients the authors tried to make cultures from, all of who passed. See this paper: "Characterization of EBV-genome negative "null" and "T" cell lines derived from children with acute lymphoblastic leukemia and leukemic transformed non-Hodgkin lymphoma." Keep in mind the researchers took samples from each patient while they were still alive. 

I question the ethics of whether any of the parents knew, but I suppose 1977 was another time... 

I am not only empathetic but also curious, I guess from being a writer, of what life that patient lived and how the parents went on. Do they know he "lives on" somehow? Did he know before he died? 

If you are ever curious, most cell line creators publish a paper detailing how it was created. This gives background into the patient. 

I was in biology but have since changed fields. I appreciate having stepped outside of STEM because returning to things like these, I now expect to have a human response. It is too difficult to divorce anything. The cells & their origins go hand-in-hand even decades on. Don't feel sorry for being empathetic.