One of the major themes in Mary Shelley's Frankenstein, is the failure to assume parental responsibility. Victor Frankenstein's refusal to nurture the creature he has created sends the creature out into a cold and cruel world that will bring him nothing but pain and heartache.
Once Victor flees from the creature he has brought to life, the monster is driven out of society. He finds himself alone, searching for ways to survive: how to eat, keep warm and find shelter. He is like a newborn child with the mind of an infant. It does not take him long to realize that he needs to hide to avoid being beaten or killed.
In Chapters Twelve and Thirteen, the creature discovers the homestead which is being rented by the DeLacy family: Felix, Agatha, and their father. While they are very poor, they all greatly love each other. In Chapter Thirteen, Felix's sweetheart, Safie, comes to stay with them, also having no money—and nowhere else to turn.
In watching these people, the creature comes to understand the concept of family (among many other things, as he listens to Felix teach Safie, who knows little of the language, etc.). The creature realizes that his creator has abandoned him, but deeply desires to be accepted for who he is and loved regardless of his physical appearance.
The gentle manners and beauty of the cottagers greatly endeared them to me: when they were unhappy, I felt depressed; when they rejoiced, I sympathised in their joys.
This becomes a central theme in the story (in terms of acceptance vs. loneliness and isolation), as the creature struggles to find his place in the world.
I admired virtue and good feelings, and loved the gentle manners and amiable qualities of my cottagers; but I was shut out from intercourse with them, except through means which I obtained by stealth, when I was unseen and unknown, and which rather increased than satisfied the desire I had of becoming one among my fellows.
To become a part of this family, the creature starts by trying to befriend the DeLacy family, but his appearance so horrifies them that Felix beats him away, and the family suddenly leaves, never to return to the cottage.
Later the creature tries to force Victor to make him a mate so that the monster does not need to live out his life completely alone. And while Victor can understand the creature's need for companionship, he cannot bring himself to replicate the experiment that gave the monster life. In this, the creature becomes enraged, swearing that Victor will know no peace or happiness because he has robbed his creation of his only opportunity for happiness. The monster kills almost everyone Victor loves. Knowing that he will have no friendship or love, the creature would prefer Victor's hatred and desire for vengeance, rather than spending the rest of his existence separated completely from society. After all, being hated is better than being ignored (or so the creature sees it).
Once Victor is dead, the monster has nothing to live for, and he goes off to die.
All of this ties in to the need of all creatures for companionship of some kind. Chapters Twelve and Thirteen introduce the need of social connections for all living creatures. As this is denied him, the rest of the story describes what the monster is driven to because he is forced to live without the camaraderie or the society of human beings.