The bottom two images (three photos) make plausible matches, though age difference would have erased some commonalities. Yet age difference does not account for the fact that the mustachioed man has a wide mouth while the youthful cowboy has a narrow mouth.
If we accept that the mustachioed man is the real Billy the Kid (that man sought the New Mexico governor's pardon in 1949), then the image of the lone youthful cowboy probably is not. That is, the accepted photo of the real Billy may date back to the old West years in Lincoln County, New Mexico, but it would not be an authentic image of Billy the Kid.
As for the other image with the "wrong" ear curvature, that might be accounted for by a slight variation in camera angle. But then there's that rather large nose which doesn't match the one on Mustache Bill. In fact, it looks a bit cockeyed, as if inexpertly pasted on with the evidence of tampering smeared out by some blurring of reflected light.
