These siblings share the same miserable childhood, have similar temperaments – an exaggerated capacity for anger and a hefty amount of pride – and even love the same woman. But while Esteban enjoys a "destiny that [is] bright, free, and full of promise," Férula has to stay locked up at home, tending to their sick mother. Esteban gets to get married and gets to sleep with Clara, while Férula can only spy on them from behind the bedroom door.
The rivalry that exists between Férula and her brother Esteban basically boils down to this: both siblings desire the same things out of life, but only Esteban can have them because he's a man. This doesn't reflect so much on Esteban's character as it does on the social expectations and constraints for women at the time. Férula sums it all up when she says this: "I would like to have been born a man, so I could leave too" (2.19).
Remember all those societal constraints that hold Férula back in life? She's always complaining about being a woman and not being able to leave home, seek her fortune, or get married. Well, meet Tránsito Soto, the woman who puts Férula and her excuses to shame.
With a lot of ambition and just a teensy bit of help from Esteban Trueba, Tránsito makes her way from a dirty country brothel to the big, glitzy capital, where she revolutionizes the escort industry and starts a cooperative of sex workers. She's had it up to here with "daughters of rigidity" who cling to patriarchal tradition even when it holds them back (and straight-laced Férula is a classic example of this).
When Alba gets raped by Esteban García, she's furious at first. Just like Pancha, she vows to avenge herself on the man who violated her. Like Pancha, Alba winds up pregnant with a child who might be the offspring of the rapist. But, unlike Pancha, who passes her resentment on to her son, and later her grandson, Alba does something really difficult. She forgives the man who raped her. Why? Because Alba doesn't want to pass a desire for vengeance on to future generations – she wants to break the cycle of hatred and revenge in order to liberate her daughter from further violence.