The Outsiders, by S.E Hinton

I don't think there is a mother-figure but Darry is cast into the role of father-figure. Darry tries hard to keep the family together and maintain boundaries for the boys. Being the big brother makes it difficult for Darry to assume a parental role.

In reality Ponyboy has never grown up with any mother-figure around him, most of the females he talks to are friends such as Cherry. Therefore he has no mother figure, his father-figure is Darry since you know he's always wanting him to make good grades, disciplining him many times within the story and always caring about him. Darry isn't really one of the main reasons the family is in a mutual relationship together most of the times. Most of the bonding is created within Sodapop calming both of them down when they argue. But since Darry is the oldest of the 3 brothers and SodaPop is the middle also dropped out, both Sodapop and Darry serve as a Father-figure to Ponyboy because they both sacrificed themselves with jobs rather than not taking care of Ponyboy. Just like Darry rejected a college scholarship just to take care of his brothers. He might not have any mother-figures within his reach, but his brothers are enough of father-figures to make him succeed.