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Your mother and sister hate your boyfriend? How genetics determines the condemnation


Professor Leif Edward Ottesen Kennair and Associate Professor Robert Biegler from the Norwegian University of Science and Technology’s Department of Psychology completed a study that has determined that genetics is the reason your mother and sister hate your boyfriend.

We’re all aware of the age-old Scenario: a young daughter brings home her boyfriend to meet the family, only to have her mother disapproval. Yet, your sister provides additional indignation of the so called “Love of your life”. If history is doomed to repeat itself, then genetics are to blame for this timeless ire. A recent study titles this the Juliet Effect a result of parental opposition to a relationship, characterized by an intensification of the romantic feelings of those in the relationship. The theory takes its name from the conflict between Juliet and her mother, Lady Capulet, in Shakespeare’s drama “Romeo and Juliet”.


A study completed by Professor Leif Edward Ottesen Kennair and Associate Professor Robert Biegler from the Norwegian University of Science and Technology’s (NTNU) Department of Psychology says it comes down to simple genetics.

In case you’re among the few of us who weren’t provided “Romeo and Juliet” as standard course material as a high school freshman: Juliet falls madly in love with Romeo, a member of the Montague family, sworn enemies to the Capulets. Despite Juliet’s longing for young Romeo Lady Capulet prefers Juliet weds Paris, a man of affluence. Spoiler alert: things do not end well for the young lovers. While this may not be news to any of us, what the study did determine was that sisters also disagree on what traits they deem fit for your potential boyfriends.

So, what’s the catch? Your mother and sister would prefer a more stoic, reliable, and (let’s be honest) boring partner for you. Yet, they would choose the fetching hunk for themselves.

“For their own partners, women focus on an attractive appearance that suggests good health and an ability to pass on their genes. At the same time, they prioritize qualities in their sister’s partner that can provide direct benefits for the whole family,” say the researchers. “This is consistent with our previous studies where we compared mothers’ and daughters’ choices,” according to Kenari and Beiger.

Several years ago, a similar study was conducted with mothers and daughters which yielded similar results. “We see a conflict between mother and daughter because of opposing interests,” says Associate Professor Robert Biegler. To no one’s surprise Mothers (and sisters) seek different qualities in their daughter’s boyfriends than the daughters themselves.

The results are in a survey which was conducted among 279 women who had sisters. The women rated the relevance of 133 traits for their own ideal male long-term partner, then their sister’s ideal male long-term partner. Although sisters agreed upon most of the traits, there are also methodical and foreseeable differences.

“Women consider traits indicating genetic fitness to be more important for their own ideal partners than for their sister’s ideal partner. Similarly, traits that might provide benefits to other, extended family members are prioritized for their sister’s ideal partner,” says Biegler.


Characteristics like being understanding, responsibility, empathy, and sensibility had greater value when considering your sister’s partner. Yet, being humorous, sexually satisfying, fun, and charming carried more significance among partners they would like to be with.

How can there be so many disparate qualities in the survey? A greater emphasis is placed on your children – a result of the partner you choose – than that of your sister’s children. Transferring your own genes is more imperative than that of your siblings, yet, evolutionary speaking, we still account for the offspring of our siblings or “Inclusive Fitness”.

Essentially, you have a greater hand in determining how your children turn out than your sister’s children but were still concerned with her children. This is where the judgment stems from.

Hypocrisy or Evolution



From an evolutionary standpoint, you share genetic material with relatives, making it difficult not to a have a stake in who they choose to partner with. This is the theory of “Inclusive Fitness”: the ability of an individual organism to pass on its genes to the next generation, taking into account the shared genes passed on by the organism’s close relatives.

“Women prefer for their daughter or sister to choose someone who can contribute to the upbringing of their own children and grandchildren, or who at least doesn’t pose a burden,” Kennair says.

Your sister or daughters partner should not interfere with your descendant’s opportunities of spreading your familial genetic makeup. The more reliable the boyfriend is, or the more well off he is, then the less likely he will be to burden the family as a whole and limiting the potential for spreading their genes.

Ideally, your sibling’s partner should embody all the qualities conducive to passing on the family genes: financially strong, fatherly, trustworthy, and of an acceptable social status that can benefit the genetic inheritance; at the very least they cannot restrict it.

Do as I say, not as I do


When it comes to choosing your own partner, things are a bit different. Attraction and physicality trump intelligence and reliability.

“The underlying truth remains: passing on your own genes is the priority. The primary consideration is to find a partner who can give you attractive children who survive,” said Kennair “A healthy hunk is presumably in good health, attractive to others as a partner and can transfer those genes to your children.”

Granted, your children can still be attractive if you choose the proverbial “Geeky” guy, but we instinctually lean towards what we consider genetically superior on a physical level. That’s not to say the physical aspect will always determine our choices; the enduring debate of nature vs nurture should be considered as well.

So, while your sister may condemn that “slacker” boyfriend of yours, on a subconscious level she may be drawn to the very same type of guy.

I choose you?

There is no guarantee one way or the other on how — or more importantly – who you choose to be with. Many of us live in individualistic societies, cultures oriented around the self, being independent instead of identifying with a group mentality.

However, your family can often be the greatest influence in your life. Your sister or mother may influence your decision through both direct and indirect action. They may choose to passive aggression, directly approach you on the matter, refuse financial assistance or cut you off entirely if you choose the aforementioned heartthrob. Whether you elect to agree with them is another matter. 

What’s inside

The results of the study tend to elicit negative responses from detractors. Kennair and Biegler say it isn’t a matter of morality, rather it is only the evolutionary result of our desire to pass on genes.

“People who haven’t behaved according to this pattern have been deselected through generations. A larger proportion of them simply didn’t get to pass on their genes to a new generation. So, their contribution to the gene pool dwindled,” says Kennair.

Ideally, your mate has many of the qualities women choose for themselves and for their relatives. But if we’re being honest, no one is perfect. Our love for a boyfriend may blind you to his misgivings or quirks; maybe we even accept them because the entirety of his being is respectable. However, your sister will expose those undesirable qualities like a slide under a microscope.

The abhorrence your sister or mother may have for your boyfriend stems from an innate mechanism within us. Your mother and sister are, in fact, human and have the same desire to seek out the best possible partner. The mechanism may be dormant or subconscious, but it exists none the less.

What now?

The study serves as an insight to explain our innate reactions to one another. In this case, it can provide some understanding as to why we tend to witness the same scenario playing itself out: disapproval of who a daughter chooses to be with. By no means does this mean your sister and mother are out to take your boyfriend for themselves or undermine your relationship. The thought alone stirs up a collective gag reflex.

However, studies like this allow us to discover our humanity. Granted, the study would require further research to solidify its findings, but it is a first step in understanding the basis of human interaction. A little insight can go a long way.

Novoa B