Prince Erik, duke of Västmanland, suffered from a mental retardation, which is said to have been caused by his mother's medication during the pregnancy. He also suffered from epilepsy. Prince Erik was very seldom seen in public.
It is said that he sometimes acted very strange, but most of the time he led a quiet, calm life. He died of the Spanish flu (I am not sure if this is the correct English name for the influenza that struck Europe after World War I and killed millions of people). His mother queen Victoria is said to never have been able to forgive herself for not being by his side when he died.
I have a most charming picture of prince Erik in a book. I wish I could post it here, but unfortunately I do not have a scanner.
It is showing him from the side, and believe me, he seems to have been very good looking.