Ambrose Monk is the brother of Adrian Monk.
Ambrose, like his brother Adrian, possesses uncanny powers of deduction and memory. Unfortunately, he suffers from a severe form of agoraphobia. As of 2003, he had not left the home he grew up in since 1971.
When Adrian and Ambrose were children, they shared a strong bond with their father. This may have been due to his strict rules, such as not ever entering his office, and the boys' social seclusion, causing a sort of dependency. One day, while going out to pick up some Chinese food, Jack Monk left his family. Ever since, Ambrose has been obsessed with the idea of his return, even to the point of preparing a dinner plate for him every night, just in case. It is stated in the series Little Monk that Ambrose was born 2 years before Adrian, in 1957. It is also said that Ambrose never talked as a child, and even performed mime for a school talent show because of this. He was not agoraphobic in his youth and regularly left the house. He also implies that his father named him after his pet turtle when he was born.
The house he lives in is cluttered piles of newspapers, and filing cabinets which are stuffed with his father's mail spanning the entirety of his father's absence. He also kept his father's study exactly the way Jack left it. A sore spot between brothers was that Ambrose believed Adrian, being a first rate detective, should use his abilities to track down their father. Adrian admits that he could possibly find him--but has no desire to do so.
Ambrose and Adrian lost their mother in 1994, after a very long illness.
As a means of supporting himself, Ambrose writes owner's manuals for many different consumer products in multiple languages which he taught himself. As of 2003, he was fluent in seven languages and was teaching himself an eighth (Mandarin). Other than Mandarin and English, the only languages that we know he has taught himself are German and French. (He tells Sharona that he made a very tiny mistake on page 42 in the German section of one of his manuals, and he greeted Natalie in French when they met.)
He thinks that Adrian is a daredevil, as he went into stores to buy things when he was 15, drove a car when he was 24, and went on a date when he was 26.
Ambrose was estranged from his brother for a period of about seven years, following the death of Adrian's beloved wife, Trudy. Ambrose blamed himself for her death, since at his request Trudy was out buying him cough medicine when she was murdered by a bomb planted under the front seat of her car. Guilt-ridden, Ambrose avoided all contact with Adrian for years after the incident, despite numerous phone calls and letters from Adrian. After a time, not knowing why Ambrose had seemingly abandoned him, Adrian became so angered with his brother that he went so far as to pretend he did not exist, telling others he was an only child.
The two brothers would finally reconcile after Ambrose called Adrian's assistant, Sharona Fleming, and asked for Adrian's help solving a case. Ambrose believed his neighbor, Rita Van Ranken, had been murdered by her husband, Pat. Adrian and Sharona decide to investigate. Prior to solving the case, Ambrose explains why he cut himself off from his brother, and Adrian realizes how mistaken he had been. Van Ranken, becoming aware that a crucial piece of evidence linking him to his wife's murder is within Ambrose's home, sets the house on fire. Adrian arrives and forces Ambrose to emerge from the home (with the evidence, a shell casing, intact). Before returning to the house, Ambrose goes with Adrian to leave some flowers at Trudy's grave.
Less than two years later, on Halloween, Ambrose joyfully receives a phone call from his long lost father. Jack explains that he will be in town that day and would like to drop by and see his sons around 8:00 that evening. Adrian and his new assistant, Natalie Teeger, and her daughter, Julie Teeger, all come to Ambrose's house to await Jack's visit. Ambrose expresses interest in Natalie and she politely declines. As 9:00PM rolls past and Jack still does not arrive, Adrian reaffirms his belief that Jack is not really coming.
Unfortunately, they get drawn into a murder mystery when someone dressed as the Frankenstein's monster first tries to steal Ambrose's candy bowl and then steals candy from several neighborhood children who stopped at Ambrose's house. Adrian manages to link the thefts to an earlier homicide at a local convenience store. Adrian and Natalie learn that the store had delivered a candy bar to Ambrose's house, one that had been poisoned by a man named Paul Gilstrap who had hoped to murder his wife. Before they can tell Ambrose, however, they find that he has apparently eaten the poisoned candy bar. Ambrose calmly accepts the news, knowing there is no antidote. The others call an ambulance for him and soon all three are rushing towards the hospital. En route, however, they realize that the candy bar Ambrose ate was not poisoned (merely expired). Happily, they return to the house, where they find a note pinned to the door. The note is from Jack Monk, who writes that he does not blame them for not waiting up for him--and that he is proud of Ambrose for leaving the house.
In the novel series (set after the conclusion of the television show) Adrian attempts to help Ambrose overcome his agoraphobia- together they purchase a mobile home, something that allows Ambrose to see the world yet STILL remain inside if he wish. On his first vacation in 30 years, Ambrose also meets a young woman named Yuki- who becomes his personal assistant and eventual love interest. Although Adrian Monk initially disliked Yuki (since she has tattoos that don't match) he is impressed by how much the relationship changes his brother.
In the mystery novel by Lee Goldberg, Mr. Monk In Outer Space, it is revealed that Ambrose is a huge fan of the cancelled television series, Beyond Earth, a Star Trek parody, so far that he has written books on how to speak a fictional language called Dratch. It is hinted that Ambrose might speak Sanskrit. 
Ambrose also seemed to not like Christmas much, as he once attempted to lock himself in the basement during the Christmas season in 1964.
Background Information and NotesEdit
- Ambrose Monk is apparently a homage to Mycroft Holmes, the older brother of Sir Arthur Conan Doyle's famous detective Sherlock Holmes. Mycroft was also written as being more intelligent and better at deduction than his younger brother, but lacked any ambition or energy to follow through with his theories, thus rendering him useless as a "true" detective.
- While only speculation, it is possible that Ambrose cared for the boys' mother at home, as Adrian comments more than once she was sick for a very long time but did not pass away until 1994.
- Although Ambrose is supposed to be older than Adrian by a few years, it should be noted that his actor John Turturro is actually a few years younger than Tony Shalhoub.