One of the Greasers’ most important rules is “Stick together.” Why was that rule doubly important for the Curtis brothers?

The Greasers are a close-knit group of friends who go out of their way to support and protect each other. The members of the Greaser gang are willing to risk their lives for each other and act as surrogate family members.
In regards to the Curtis family, the three brothers are forced to stick together after tragically losing both of their parents in a car wreck. Darry, the oldest brother, begins working two jobs to support Sodapop and Curtis. Darry plays the guardian role and not only provides for his younger brothers but also makes sure they are safe and successful. Sodapop provides comic relief to the family and acts as a mediator between Darry and Ponyboy. Ponyboy is the youngest brother, who eventually gains perspective and appreciates Darry's sacrifice to keep their family intact.
Given their difficult, unfortunate situation, the Curtis brothers are forced to look out for one another and stick together. Following Bob Sheldon's death and the church fire, the Curtis brothers risk being split up by the court system. Fortunately, Darry is perceived as a responsible adult and Pony is an excellent student, which helps sway the judge's opinion to keep their family intact. In order to survive and thrive in the rough city without parental guidance, the Curtis brothers stick together and support each other in every endeavor.