[blinddev]

The fact that the real Erwin van Haarlem seemingly vanished is suspicious. I would assume you would only want to assign an identity of someone who is known to be dead, yet the orphanage apparently sent many letters to the mother. Assuming that's true, of course.

[Lordarminius]

I assume he may have died later in life, maybe late childhood

[pvitz]

Spoiler: The real one was adopted and met Johanna later. Source: The story can be found on Kindle Singles, but the BBC article contains basically everything interesting already.

[sulam]

So why weren't there two of them? Or were there and it never became an issue?

[pvitz]

The real one got adopted when he was four years old and his new parents "raised him as their own." He found out about the adoption a long time later. Therefore, it is safe to assume that he also had a different name.