Modified Humans

Modified humans are humans who have been biologically modified through genetic enhancements to have enhanced physical traits.

Appearance
Modified humans are basically normal humans with artificial enhancements made at a genetic level. So far, the only known modified humans are four of the five children of the Vinsmoke Family. Their external appearances are identical to that of normal humans. Their genetic enhancements also caused change to their hair colour as shown that aside from Sanji who modifications seem to have been negated, none of the Vinsmoke children inherited their parents's hair colour.

Modified Humans

 * Vinsmoke Reiju
 * Vinsmoke Ichiji
 * Vinsmoke Niji
 * Vinsmoke Yonji

Biology
Modified humans are humans whose Lineage Factor has been manipulated, usually at the embryonic stage. By manipulating this "blueprint of life", the growth of the life form in question can be changed accordingly.

Vinsmoke Judge engineered his four sons to possess superhuman traits, by applying the procedure onto them during their fetus stage, against the wishes of his wife, Sora. By doing so, he ensured they would develop a secondary, hardened skeleton known as an Exoskeleton (外骨格), lose their capacity for empathy or compassion, have an increased healing ability, and (with training) rapidly increase in strength and resilience to the point equalling an adult man while in their early childhood.

Vinsmoke Sanji seems to be the the only one of the four Vinsmoke quadruplets who did not gain any of the genetic enhancements his father attempted to imprint onto him, due to his mother taking in a powerful drug in an attempt to negate the surgery's effects. Although Ichiji, Niji and Yonji all adapted to their father's engineering, while it seems the drug rendered Sanji alone a "normal human".

Vinsmoke Reiju, although not born alongside her four brothers, was also modified by her father to possess such enhancements, but with some alterations: she cannot disobey direct orders, but retains her emotions and can circumvent his orders with loopholes.

Cultural Relationships
Modified humans bring up the issue of benefits versus ethical considerations: while Judge was adamant of turning his four sons into superhuman commanders for his Germa 66, Sora was against the idea of negating their ability to feel compassion. Sora fiercely believed that such modifications would render their sons to be inhuman, and she went as far as to intake a powerful drug in an attempt to negate these modifications, which only worked on Sanji in exchange, the drug caused permanent damage to Sora's health leading her to weaken until a premature death several years later after she ingested the drug. Reiju who was born three years earlier than her brothers was subjected to a different variation of genetic enhancements which similarly gives her limitless superhuman physical potential and an Exoskeleton, she retains her innate capability to feel empathy and also due to Sora's parenting which emphasis on compassion instead of militarism, Reiju alongside Sanji became the only ones of the Vinsmoke children to have kindness and compassion.

Due to their lack of compassion and upbringing, the three male modified humans of the Vinsmoke Family look down on others with a royal haughtiness, and are willing to kill and injure in cold blood, and even in a sadistic sense, such as ordering soldiers to sacrifice their own lives or brutally attacking a devoted chef to vent out frustrations. Their cruelty extends even to their brother, Sanji, whom they see as a failure due to his failure to adapt to the genetic modifications and retaining his humanity. While they usually demonstrate loyalty to their father and kingdom, they later prove to be completely heartless towards him as well, willing to allow him to be murdered without a shred of care.

The removal of emotions in Ichiji, Niji and Yonji, however, have rendered them to be incapable of fearing even death. While Judge had intended this to make them efficient combatants and killing machines, it can prove to be a great flaw. When they were surrounded by the Big Mom Pirates and restrained at gunpoint without weapons, they assessed quickly that there was no way to retaliate, defend or escape, and so simply sat there unconcerned, appearing to accept death nonchalantly. The three even went as far as to joke about and label their own father (whom they usually respect) as pathetic for pleading and crying. This indicates that the three act logically in a machine-efficient manner, never taking sentiments (even regarding their own lives) into account. Judge, witnessing this flawed design in their genetic engineering, desperately thought that something was wrong with them.

Overall Strength
The modified humans engineered by Judge possess an exoskeleton, which grants them enhanced durability, leading them to be renowned for their "iron bodies". They also possess an increased healing rate, as Reiju managed to heal within hours of Charlotte Pudding shooting her left leg with special Candy Jacket bullets. With training, their strength and resilience would rapidly increase to the point equalling an adult man's, while in their early childhood. Further administration of drugs can also further the augmentations.

Judge also modified his sons to lose their emotions of empathy and compassion, in order to increase their combat efficiency. Because of this, the three sons who adapted to the modifications are utterly incapable of sympathy for people outside of their family, instead believing themselves above all others; Reiju considers them to lack humanity as a result.

Reiju and Niji have both demonstrated special abilities similar to Devil Fruit users, from which were derived their individual enhancements: Reiju's ability ("Poison Pink") allows her to suck out powerful poison out of an afflicted individual via kissing  secrete poison to attack enemies and also neutralize within her body,demonstrating complete immunity to the deadliest poison an ability which is unique to the Doku Doku no Mi; Niji's ability ("Electric Blue") allows him to generate electricity from his body similar to the Goro Goro no Mi.

Limits
The Exoskeleton, while powerful, is not invincible. A powerful enough force can cause it to dent, although it can be repaired with a counter blunt-force, such as a hammer or a "Press Machine". Should something like the jaw be dislocated, the modified human in question can rearrange it by hand. The special "Candy Jacket" bullets utilized by Pudding managed to pierce through Reiju's exoskeleton, causing her left leg to bleed profusely.

Modified humans are as vulnerable to Devil Fruit powers as any other normal human, as Reiju's memories were successfully modified by Pudding without any difficulty.

Additionally, Judge's removal of his three son's emotions has caused them to have no fear of death to the point of even laughing at the prospect of being killed by the Big Mom Pirates and showing no sympathy for their father when he cried at the idea of being unable to fulfill his dream of ruling the North Blue, causing Vinsmoke Judge to say their was something wrong with them, failing to realize that it was his modifications to them that made them that way, as noted by Reiju. As she had never been modified in the way her brother's had, Reiju retained her emotions and humanity to the point of secretly adopting her mother's compassion for the weak, while maintaining a facade that she respected her father and embraced her family's royal status, while in truth, she came to despise her father due to his role in their mother's death, robbing her three brother's of their humanity, and mistreatment of her younger brother Sanji who retained his humanity due to her mother's actions. Reiju herself however is forced to remain loyal to her father in order to carry out his ambitions apparently due to certain modifications Judge had made to her, which while preventing Reiju from directly opposing her father or family, doesn't stop Reiju from undermining them indirectly as she replaced Sanji's exploding wrist bracelets with fakes, showing she retains some autonomy and free will. Due to her sense of morality, she sees herself, her father, and her three brothers as murderers who deserved to die as she believes their kingdom as nothing but a war machine, though believed that Sanji did not deserve this fate due to his compassionate nature. As a result, Reiju does nothing to warn her family that Big Mom is planning to betray and kill them to steal their Kingdom's cloning technology, despite Sanji revealing it to her after Pudding altered her memories, as she believed the world would be better off, while telling Sanji to save himself.

It is shown that though Judge viewed Sanji as a failure due to his compassion and humanity thanks to his wife's sacrifice, it was Sanji's human compassion that lead him to rescue his family despite the years of mistreatment they caused him, an act that shocked Judge and moved Reiju who silently thanked him for proving their bloodline was not completely corrupt.

Their natural personality however cannot be genetically modified as seen all of Vinsmoke Judge sons shares one natural personality which was lecherous as they become lovestruck the moment they saw Nami.