The twins are assassins and spies apart of Spider.
The twins were students of Lady Browning's Preparatory Academy For Girls' secret program, studying as assassins and spies. They are not students as of the Academy's exposure to the public.
Lil' Miss Malachite is Melanie and Miltia's mother. The twins share a close relationship with their mother, who is concerned about their safety enough to hide them away during a gang war between Spider and The Mouse and the Parrot. Lil' Miss trusted the two with her plans for Spider, and Melanie in particular took after her mother, something which Roman noted.
They referred to Lil' Miss by name or called her "Mother".
Miltia is Melanie's twin sister. They share a close relationship and are always seen with each other. In battle, they sync their movements and strikes to creating a flowing tag team combo. They often finished each other's sentences and "read each other's mind", creeping out Roman, and called each other "Mel" and "Mil," respectively.
The Twins and Roman met when they were children. They advise Roman on his ambitions whilst he serves as their guardian during a gang war. Roman tries to use them as hostages to sell out when he tries to betray Spider, but his bond with them is greater than his greed. As a result of this, their relationship with the 22-year old is soured, and his later attempts to flirt with and charm them to avoid being killed by the two is shown to be fruitless.
When Roman and Melanie enter the Mouse and Parrot hideout, a member asks if she is the man's girlfriend, which he doesn't make an effort to refute. This disgusts Melanie.
Junior was Melanie's superior. Melanie, along with Miltia, were Junior's bodyguards, as she constantly followed him. Her loyalty was not as strong as her sister's, only reluctantly following. They both defended his club when Junior was attacked by Yang Xiao Long.
The Twins were originally bullies of Neo, who they knew as Trivia Vanille, pulling pranks on her and getting away with it due to their popularity. When Trivia joined the academy's secret program, the two bonded with Neo much more, becoming close friends with one another. However, when Neo betrays Spider and joins Roman Torchwick, it appears their relationship is strained. Neo was seemingly afraid of their skill, choosing to escape rather than fight them.