Identikit got pretty close and there weren't that many bits in there and quite a few of them were hairstyles and that's a choice, not genetics. How many head shapes, noses, eyes, mouths and ears can there be?
A few million? Then everybody has a few thousand doubles. 100 Million? Still 80.
I once had a waiter in a restaurant that I'd never been to before swear he'd seen me there many times, and when I denied it he was backed up by some of the other staff. Creepy, to say the least. Afterward I realized I should have given him my phone number and told him to call me next time "I" came in, so that I could meet my doppelganger.
So even finger prints are unreliable.
The definition of "match" is complicated, and not just for issues like partial fingerprints and blurring. The FBI says they had a "100 percent match" in the Mayfield case. The judge says this assessment was "fabricated and concocted by the FBI and DOJ".
Or from https://www.science.org/content/article/forensic-experts-bia... published in 2022:
"When police retrieve a print from a crime scene, they consult an FBI computer database containing millions of fingerprints and receive several possible matches, in order of the most likely possibilities. Dror found that experts were likely to pick “matches” near the top of the list even after he had scrambled their order, perhaps because of the subconscious tendency to overly trust computer technology.
“People would say to me fingerprints don’t lie,” Dror says. “And I would say yes, but it’s also true that fingerprints don’t speak. It’s the human examiner who makes the judgment, and humans are fallible.”"