Clara was extremely precocious and had inherited the runaway imagination of all the women in her family on her mother's side. (1.4)
Inheritance is a motif in the novel – Clara, her sister Rosa, and all of Clara's female descendents share a vivid imagination and an aptitude for expressing themselves creatively. Even Blanca's general practicality doesn't keep her from developing an artistic streak.
All her life she would remember the afternoons spent in the company of her mother in the sewing room, where Nívea sewed clothing for the poor on her machine and told stories and anecdotes about the family. (3.11)
Mothers and daughters bond over storytelling – this is something else that gets passed down through the women of the family from generation to generation. Nívea and Clara, Clara and Blanca, and Blanca and Alba all repeat the ritual of sharing family anecdotes. We can only suppose that Alba will do the same with her own daughter.
They buried her in a special plot in the tiny graveyard alongside the abandoned church, at the foot of the volcano, because she had been the patrón's wife, in a manner of speaking, since she had given him the only son who bore his name, though not his surname, and a grandson, the strange Esteban García, who was destined to play a terrible role in the history of the family. (4.104)
Legal marriage and paternity are not the only ways we can understand "family" in this novel – whether he likes it or not, Esteban's relationship with Pancha García produces another branch of his family.
In the lovers' postures he could see the abandon typical of those who have known each other for a long time. What he was looking at did not at all resemble an erotic summer idyll, as he had supposed, but rather a marriage of body and soul. (6.50)
Though, as far as we can tell, Blanca and Pedro Tercero are never legally wed, they're far more intimate with one another than Esteban and Clara, or than Blanca will ever be with Jean de Satigny.
Clara never spoke to her husband again. She stopped using her married name and removed the fine gold wedding ring that he had placed on her finger twenty years before… (6.64)
Even though Clara and Esteban Trueba remain legally married, for all practical purposes they're divorced. The legal status of relationships in this novel doesn't seem to matter as much as emotional connectedness and communication.
Clara was very happy to be living with her sons and was determined to establish a friendly relationship with them. She had had very little contact with them when they were small, and in her haste to see them "become men," she had lost the best hours with her sons and been forced to keep all her tender feelings to herself. (7.7)
Mothers and daughters tend to have stronger relationships in this novel than mothers and sons (or fathers and sons, for that matter). In fact, the social injunction to raise young boys to "become men" might be the reason we see so many male characters that have trouble expressing their emotions and forming intimate relationships with other people.
"Be quiet!" he roared. "You're getting married. I don't want any bastards in the family, do you hear me?"
"I thought we already had several," Blanca replied. (7.28)
Blanca finally talks back to her dad and points out his hypocrisy in condemning her for having sex outside of marriage. Aside from being monumentally sexist and unfair, Esteban's attitude is also dangerous. His limited conception of "family" is what causes him to ignore the offspring he's sired outside of wedlock as well as the resentment that they feel towards him and his "legitimate" family.
Esteban Trueba […] ended up shouting and slamming doors because, as he put it, he was up to here with living among a bunch of lunatics and all he wanted was a little normality, but he had had the misfortune of marrying an eccentric and siring three good-for-nothing crazies who were ruining his life. (7.55)
Esteban has rigid ideas about what a family and a society should look like, and he's constantly trying to get his own family and his own society to fit that mold. His perpetual rage can be attributed to the fact that things never go exactly according to his plan. His dreams of "normality" elude him.
Once a week, on Saturday, they all dined around the great oak table that had always been in the family and had first belonged to the del Valles. […] The child watched the adults in fascination. There was her radiant grandmother, her teeth in place for the occasion, sending messages to her husband through her children or the servants; Jaime flaunting his bad manners by burping after each course and picking his teeth with his little finger to annoy his father; Nicolás with his eyes half closed chewing every bite fifty times; and Blanca chattering about anything she could think of just to create the illusion of a normal meal. (9.28)
The weekly meal, with all family members in attendance, provides a snapshot of familial relations in the Trueba household. They may seem dysfunctional, but each person has his or her role. Notice that the two family members who get along with everyone are Clara and Alba – they're the glue that keeps the family together.
Only his grandmother had paid him any attention, and she never let him forget that he was different from the others because the patrón's blood ran in his veins. (9.64)
While Esteban Trueba may forget about Pancha García, she clearly never forgets about him, his cruel treatment towards her, or the way he neglects their son. The hatred she feels for the patrón is one thing that she passes down to their grandson.
My mission is […] simply to fill these pages while I wait for Miguel, while I bury my grandfather, whose body lies beside me in this room, while I wait for better times to come, while I carry this child in my womb, the daughter of so many rapes or perhaps of Miguel, but above all, my own daughter. (Epilogue.45)
Unlike Pancha, who raises her descendents on stories about the injustice she suffered and stokes their desire for vengeance, Alba decides to forgive the men who tortured and raped her. When we realize that she, too, bears a child who may be the product of rape, it becomes clear why such forgiveness is necessary – to break the "terrible chain" of vengeance and liberate her descendents from an endless cycle of violence.