It’s being speculated that this could also be a younger version of a current character to be used for flashback scenes.
Not many characters remaining come from poor backgrounds, save Varys, who, since the beginning, has operated of the interests of the realm above all else.
That could just be wishful thinking from the fanbase, since it’s not as though casting calls are to be treated as gospel truth.
Perhaps the series is looking to go back to the fateful moment when he lost his genitals, to show us exactly what he heard from that fire?