Sanji, who's genetic modifications were initially negated by his mother taking a drug while he was in the womb, is unique among his siblings, both because his hair color is the same as his parents', and because the spirals on his eyebrows are on their left, rather than their right. However, genetic enhancements can cause changes to appearance not inherited from one's parents, as none of the Vinsmoke children (except Sanji) inherited their parents' hair colors, and all share the feature of both of their eyebrows curling into a spiral on one side. Their external appearances remain identical to that of normal humans.

Modified humans are normal humans with artificial enhancements made at a genetic level.