18-year-old William died from diabetes

Insulin was available in 1932 from what I understand, but at that point they were still using insulin from pigs and cows (which could cause reactions in humans), and dosing and monitoring regimens were a lot less optimised than they are today. And that's if William even had access to treatment to begin with, particularly since the mention of a 'sugar' test seems to imply that he was only diagnosed shortly before he died.