- Nellie O'Malley: Niece.
- Bridget O'Malley: Niece.
- Jenny O'Malley: Niece
- Nellie's Father: Late brother.
- Nellie's Mother: Late sister-in-law.
Mike is the brother of Nellie's father (it is never specified if he is older or younger). He is a drunkard and abandons Nellie, Bridget, and Jenny after the loss of their parents. When he sees Nellie again, he threatens to take her away and make her work in a factory for him. He is also a liar as seen when he tries to feign emotion towards the O'Malley sisters. He is completely untrustworthy and goes as far as trying to bribe money out of the Edwards to sign away his rights. He does not appear to have much of a work ethic; the foreman at his job had to yell at him to get him back on task, he is willing to force all three girls into work and take any money they would earn, and attempted to talk Gardner into paying him to sign away his rights to the O'Malley sisters. He is a bully but is easily cowed if he doesn't think he can get away with what he's doing. He calls Nellie "Nellie-girl" as a pejorative. He is pictured as unkempt and rough.
Mike is a pervading force throughout Nellie's Promise; his threat of taking the girls away from the Edwards scares Nellie into trying to leave New York, but also motivates her to seek a school more to her liking.
In the Books
Meet Samantha: An American Girl
Nellie offhandedly mentions that she stayed with her uncle while her younger sister was being born; this is most likely Mike.
Changes for Samantha: A Winter Story
After the death of Nellie's parents, Uncle Mike takes the girls in. He then takes their money and leaves them to starve and freeze to death, leading to their going to Cold Rock House.
Early in the book, Nellie walks past a group of men doing road work. One of the men stops and grabs Nellie by the arm roughly. It is Uncle Mike. He snidely remarks on her fine appearance, saying that Nellie has clearly found some well off people to care for the girls. He asks where they live and Nellie doesn't answer. Uncle Mike calls her a stubborn brat and threatens that he'll find out where she is. He'll take the girls away to live with him as he has that right, and that once they do so, he'll put them all in the factories to work for him. Nellie screams not to come near them, then stomps on his foot to twist out of his grasp and run away. Uncle Mike stars to give chase after Nellie but falls over his wheelbarrow; the crew boss yells at him to get back to work. Mike shouts after the running Nellie that she belongs to him. These words bother Nellie as she runs all the way home.The secret of Mike's reappearance bothers Nellie severely through the book. When Nellie takes Cornelia and Samantha to the settlement house and suspects she has seen him, she ends up leading Cornelia and Samantha off and down a rough alley. He later goes to the settlement house and tries to get information on the whereabouts of the O'Malley sisters, but Miss Brennan runs him off with no information. This near scare motivates Nellie to try and leave town.
After explaining her secret about Mike to Samantha, Nellie and Samantha go down to breakfast. Nellie hears voices and freezes, grabbing Samantha's hand—one of the voices is Uncle Mike, and Nellie is sure he's come to take the girls away. When Nellie decides to face him and greets Uncle Mike, he is slouched in a chair. He says he's found her. Gardner corrects Mike--they found him, and he's here because he was asked to be. Uncle Mike growls that he was chased by a detective and dragged there. The Edwards have been looking for Uncle Mike since they took in the three girls to talk to him about adopting them. They found him a few days ago and when Nellie mentioned going to Boston, they felt they should speak to him sooner rather than later. Uncle Mike tells Nellie she's been keeping secrets and she didn't tell the Edwards that he and Nellie ran into each other already and he swore to take them back. The Edwards explain that Uncle Mike can sign papers giving up his rights to the three girls and allowing their adoption; he won't be able to see them any more once he signs over his rights. Uncle Mike crosses his arms and says that he may or may not sign the papers. The children are his late brother's and not seeing them anymore would be a loss. He then tries to bribe the Edwards, saying they could pay him into signing and then blatantly asks Gardner how much they're worth to him. Nellie steps in and tells him that he had better sign the papers and not ask for money. Uncle Mike smirks and questions her. When Nellie threatens to go to the law and tell what he did to the girls, Uncle Mike is shocked for a moment. He snatches the pen and scrawls his signature hastily on the paper. He then jams his hat on his head and says good riddance to bad rubbish. He shakes his fist angrily and says he hopes he never sees any of them again as long as he lives before slamming the door behind him.
Uncle Mike is never seen again.
In the Film
Mike is completely removed from the film; after the death of their father, the O'Malley sisters are sent immediately to Cold Rock House.