Some of these giant skeletons were reportedly found with a 'double row of teeth,' doesn't that prove they weren't ordinary humans?

The 'double row of teeth' detail that keeps showing up attached to these 19th-century giant-skeleton reports describes a real, documented, and fairly ordinary condition: hyperdontia, the growth of supernumerary (extra) teeth, a well-documented but uncommon condition, and the closely related, much more common experience of a child's baby teeth not falling out before the permanent teeth erupt behind them, producing exactly the 'double row' appearance parents and dentists still see today. Neither has any documented connection to unusual stature, and no skeletal specimen described this way in the old newspaper accounts has ever been produced for a dentist or physical anthropologist to examine. As with the skeletons themselves, this detail appears to have circulated between local hoax and misidentification stories as a stock flourish rather than as an independently verified trait of any specific find. That's a pattern folklorists recognize: a vivid, specific-sounding detail gets attached to multiple unrelated stories because it makes each one sound more credible, not because it was actually observed.

For the real biblical question behind the giant claims (the Nephilim, Anakim, and Rephaim of Genesis 6:4, Numbers 13:33, and Deuteronomy 2), see the fuller treatment in this collection's entry on the American giant-skeleton reports. The narrower point stands regardless: Scripture never attaches a double row of teeth, or any dental peculiarity at all, to any of these figures. The only physical detail Scripture actually gives is height: the spies' 'we seemed like grasshoppers' in Numbers 13:33, and the dimensions of Og of Bashan's iron bed in Deuteronomy 3:11. So this particular folklore detail doesn't strengthen the case for giants being real (because it isn't attested of any real specimen) and it doesn't weaken the biblical text either (because the biblical text never claimed it). It belongs entirely to the unrelated 19th-century American hoax tradition, and grafting it onto the Anakim/Rephaim question reads something into the biblical text that simply isn't there.