text: The reason Fallon couldn't adopt her is he hadn't the means financially to take care of her as he was just a squire (of sorts) for Borden. Cadlow was a Lord, with obvious means to raise the child to be something other than a pauper, which Fallon clearly was. Had Fallon come forward as the twin, the secret of the trick would have been revealed and the ultimate revenge that Borden wanted to exact wouldn't have been attainable. The impact of the ending would then have been lost.