Identical twins develop from the same fertilised egg and have extremely similar genetic information, yet their fingerprints are not identical. That is because DNA does not print a finished fingerprint directly onto the skin.
Genes influence the broad tendencies of ridge formation, so identical twins are more likely than unrelated people to share similar fingerprint pattern types. But during fetal development, small differences in growth, local pressure, skin tension and position affect where ridges finally divide and end. Those developmental conditions cannot be duplicated point for point in two individuals.
A study using almost 4,000 fingerprint images from 83 pairs of identical twins found that their prints were indeed more similar, while still being distinguishable by an automatic recognition system. It is a neat example of a broader biological principle: genes constrain development, but the final structure emerges through the developmental process. Similar starting conditions do not guarantee identical outcomes.
References
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035704
https://www.nist.gov/publications/longitudinal-study-fingerprint-recognition
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