Sherlock Holmes[]
Sherlock Holmes is William's ex-arch nemesis and the only person who is his equal.
The two start out as enemies on a formal level, the mastermind criminal and the detective who wants to catch him. On a personal level, William and Sherlock get along and understand each other from the beginning, so much so that Sherlock openly admits to him that he would like William to be the criminal he's chasing. In return, William always anticipated Sherlock figuring out his identity and solving the mystery.[1]
It's later revealed that to William, their first encounter had changed his world. From the moment they met, he felt as though him and Sherlock were connected by a long-lasting friendship and that he had found the only person who could ever understand him. William forgot about the weight of his plan and even considered to quit everything to continue talking with him. These feelings were reciprocated by Sherlock.[2]
William's trust in him goes so far that he planned to entrust the world he worked for to him. He also wished for no one else but Sherlock to be at his side when meeting his end.[2] It's due to Sherlock that William is ultimately saved, an act that filled William's world with colours. Sherlock was able to show him that death is not the answer and that he can create any future moving forward.[3]
They're caring towards one another and William still indulges in teasing Sherlock.[4] Both are also seen to work well together in combat.[5] The closeness of their relationship is teased on multiple occasions by Billy[4][6] and also pointed out by Louis.[7]
Sherlock and William share a deep connection and have made a vow to live together, promising to guide each other in their atonement.[6]
Moriarty Group[]
Louis James Moriarty[]
Louis is William's only known biological family. William is very fond of his brother and ever since young, the two were always together. He has always been very caring towards Louis and worried for his condition since he was very sick before being treated. William would always affirm Louis' existence and reassure his worth in the world.
Even as adults, William remained protective of his brother. He never wanted to involve Louis in his plan, and instead wanted him to remain innocent, unlike himself. He thought it would protect Louis from going down the same path as him, but after hearing Louis' reasoning in the matter and realizing that he left his brother lonely for his own ego, he let Louis join them.
Despite that, William never once desired Louis' life and always wished for him to survive.[2]
Albert James Moriarty[]
Albert is William's older adoptive brother. William, as well as Louis, were invited by Albert to live with him and he offered all the resources he had so William could show him the vision of a more just world. Albert has always been very supportive of William's plan and William tried to reciprocate this.
The two share a close relationship and it was only in front of Albert that William would occasionally show his distress to. Albert's encouragment in those moments meant a lot to William and their vow gave him the strength to keep going. William considers becoming Albert's younger brother his very pride.
Sebastian Moran[]
Moran is considered William's right-hand man and one of his closest allies. The two share a close bond and William shows trust in Moran's abilities.
Fred Porlock[]
Fred is one of William's friends and closest allies. How they met is unknown, but Fred deeply admires William and always had faith in his grand plan. Despite that, Fred was initially afraid to voice concerns like children being hunted because he felt it wasn't of greater purpose, but William reassures him that he will be Fred's ally and have his support as long as Fred despises evil.[8]
Moran notes that out of all of them, Fred is the one most similar to William.[8]
James Bonde[]
Jack Renfield[]
Jack is William's old teacher and the one who taught him the art of killing. The two share a good relationship and Jack is quite affectionate with him, calling him "Little Will" which William does not mind. Jack shows great loyalty towards William and is supportive of his plans.
Others[]
Charles Augustus Milverton[]
After Milverton becomes involved and disrupts William's plans by murdering and blackmailing innocents, William quickly grows to detest him. After the Whiteley incident, William is determined to kill him whether his identity is made public or not. He seemingly has no empathy for Milverton and does not appear concerned when he is shot dead.
The Moriartys[]
The Moriarty family strongly opposed his and Louis' presence in the household. Lady Moriarty was especially angered and disgusted, even being physically abusive towards him, while the original William mocked the brothers and provoked his mother to lash out against them. Even the butler of the house was strict with them, frustrated he had to serve people of lower status than himself. William endured the abuse and carefully laid out preparations for the eventual murder of the Moriarty family.