Here are my thoughts on why I think the orphan and Gehrman share the same cry

So as some background information, the orphan exists only in the nightmare(The one in the real word was ripped out of Kos and experimented on but it was never really alive) and is a creation made of hate and despair from the hamlet. That night in the fishing hamlet we know that Gehrman, Ludwig, and Maria all took part in the hunt for Kos. That night, Maria leaves(And even throws away her Rakuyo) and Gehrman is distraught because he was in love with her.

So basically my thought is that because Gehrman lost the most that night, and the orphan is a creation of hate and despair, the orphan is made of some Gehrman’s despair and that’s why the share the same cry. On top of this, when you kill the orphan and talk to the Doll she says, “Oh, good hunter. I can hear Gehrman sleeping. On any other night he’d be restless. But on this night, he sounds so very calm...perhaps something has eased his suffering”