The Third Twin

Book review by
Mary Cosola, Common Sense Media
The Third Twin Book Poster Image
Popular with kids
Gripping thriller skimps on character development.

Parents say

age 17+
Based on 2 reviews

Kids say

age 14+
Based on 13 reviews

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A lot or a little?

The parents' guide to what's in this book.

Educational Value

A little information on DNA evidence, especially regarding twins. Some detail on how criminal investigations are handled.

Positive Messages

Trust your instincts -- for example, don't let other people talk you into doing things you’re not comfortable doing. Tell the truth. Don't betray the trust others put in you.

Positive Role Models & Representations

Lexi's friend Zane is a grounding presence, offering her help and good advice when she's most in need. Defense attorney Ms. Alvarez is strong, smart, and calming; she works to help Lexi and doesn't talk down to her. 


Attempted rape. Many instances of a character grabbing, restraining, or pushing someone. Fistfight resulting in minor bloodshed. Two characters push each other hard: one into a wall, the other into a sink. Descriptions of bloody murder scenes and how victims were murdered with a knife.


Making out. Kissing. Making out in underwear. Implied sex between two teens when a parent isn't home. Girls place heavy emphasis on appearing sexy to boys.


Swear words used, but not frequently, including "pissed," "a--hole," "f--k" and its variations, "bitch," "ass," "s--t," "Jesus," "p---y," "God," "bastard," and "hell."


Cheesecake Factory, Camry, Honda, Lexus, Cadillac, VW, CSI, Finding NemoAnnie, Photoshop, Baskin-Robbins, and Bank of America.

Drinking, Drugs & Smoking

Pot shown in ashtray, but character not shown smoking. Teens drink at a huge keg party. 

What parents need to know

Parents need to know that The Third Twin is a murder mystery involving twins Lexi and Ava and a fake third sister, Alicia. When the twins were little, they created Alicia to take the fall for their misdeeds. Now teenagers, they have revived the character of Alicia and use her as an alter ego to go out with boys they wouldn't normally date. When the boys start turning up dead, the evidence points toward one of the twins -- or quite possibly to the imaginary "third twin" Alicia. Characters lie and sneak out of the house. There are many instances of characters pushing, grabbing, and restraining others. Very little alcohol or drug use. Characters swear (including "f--k" and "s--t") but not frequently. Bloody murder scenes are depicted, and murder methods are described. 

User Reviews

  • Parents say
  • Kids say
Parent Written bySalsasaint June 23, 2018

Rating said ages 12+??!!!

I bought it for my 12 year old daughter. I should have read through it first. I’ve always agreed with the age limits suggested on movies and books. I take full... Continue reading
Parent of a 9, 11, and 17-year-old Written byCactusDave April 20, 2015

Not good for kids

The opening scene in this book is attempted rape. The words used in this book would make it R-Rated if it were a movie. Read the summary of each section on co... Continue reading
Teen, 16 years old Written byStephanie Y Bernal April 4, 2019

Stephanie Bernal's Review

The Third Twin is a teenage drama which includes thriller moments that make the readers want to continue reading. This novel is heavily based on mystery and rec... Continue reading
Teen, 16 years old Written byGrace9714 April 28, 2021


I would definitely not recommend this book. There was a LOT of language and sex. Even if you took all that away, it is an overall boring book. The description o... Continue reading

What's the story?

Twins Ava and Alexa "Lexi" Rios live in an affluent Southern California beach town. And though they look exactly alike, Ava's mostly interested in appearances, boys, and clothes while Lexi is studious, focusing all her energy on getting into Stanford and eventually joining their father's business. Needing someone to blame for broken household items and missing cookies when they were little, the two girls invented Alicia, their "third twin." In their teens, Ava and Lexi have brought Alicia back into their lives, going so far as to get a fake ID for Alicia and to use her as a cover to date boys and act in ways they wouldn't normally. For Lexi, in particular, pretending to be Alicia allows her to blow off steam by being bold, brash, and sexy, escaping the stress of an intense course load and always being a good kid. Suddenly, the most recent boys Alicia has dated are murdered. As Lexi becomes a prime suspect, she wonders whether the sister she knows as well as she knows herself could be the murderer. Or perhaps the imaginary third twin isn't so imaginary after all. As she tries to prove her innocence, she spins into paranoia and wonders who in her life she can really trust.

Is it any good?

THE THIRD TWIN has an interesting, compelling premise: Boys who've dated Alicia, the alter ego of twins Lexi and Ava, are murdered, always after a falling out with one of the girls. All evidence points to one of the twins -- and maybe even to the one that doesn't exist. The paranoia and fear Lexi experiences is palpable. Lexi is a likable narrator, but the book offers no real character development, and most of the secondary characters are one-dimensional. And for a supposedly smart kid,  Lexi makes a lot of stupid decisions, consistently and constantly. That flaw starts to grate by the end of the book.

The story starts slowly, but at the halfway point it picks up steam and offers a fast-paced whodunit. It's fun to read, especially when you're trying to figure out how all the pieces fit together, and the ending has a surprise twist. But, unfortunately, that twist is a little out of the blue and comes with a rushed explanation.

Talk to your kids about ...

  • Families can talk about alter egos. Do you think that pretending to be someone else would give you the courage to act in ways you might not otherwise? What are the pros and cons of such behavior?

  • Do you use social media to cultivate a certain image of yourself? What do you think of others who do that?

  • Can you think of times you faced rejection or losing but it turned out to be a good thing for you? Why might that be the case?

Book details

Our editors recommend

For kids who love mysteries and thrillers

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