Is having a Physical relationship with my sister wrong?

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In this blog post, we answer whether having a physical relationship with one’s sister is wrong. We also define the term incest and point out the biological, psychoanalytic, demographic explanations of incest.

Is having a Physical relationship with my sister wrong?

If you are having a physical relationship with your sister, you should know that is considered illegal and morally wrong in most of the countries of this world. 

The laws of many countries has deemed inscest- sibling incest or otherwise- punishable by law due to moral and ethical standards and not to mention that in most cases one person involved is an unwilling victim. 

It is also to be mentioned that incest is also considered morally wrong due to the various religious conotations that has shaped society today. These social customs are what protects the smooth functioning of society and something like incest can disrupt this functioning which is why one can expect a hugh backlash against something like incest. 

Human beings have been genetically designed to discourage attraction- physical and romantic- between siblings which is why it is very unlikely to find siblings who have sexual attraction towards each other under normal and healthy life conditons as opposed to siblings who have been reunited after separation and are in abusive and unhealthy realitonshps. 

The process of socialization between siblings in a family is part of the desensitization process to discourage attraction so as to avoid the conseques of incest that are both harmful to the people involved and the generation that might come after them.

While you might believe that what you have with your sister is something special- being part of an incestual relationship- even if it is a consensual one- can do a lot more harm than good for the both of you. 

Rather than just limiting the anger that this particular relationship is “wrong”, it must be highlighted that this relationship is dangerous. Upon being found out, you and your sibling can face the following consequence:

  • You might be arrested and jailed if incest is unlawful or illegal.
  • Face social exclusion and ostracisation
  • Develop mental health problems 
  • Genetic illnesses in your offsprings

What should I do if I am having a physical relationship with my sister?

If you and your sibling are having a consensual physical and romantic relationship, it is difficult to simply tell you to stop because what you believe and what you think cannot be influenced by social expectations. 

You and your sibling must remember that Social customs and norms allow for the smooth functioning of individuals and families within society and something like incest can disrupt the entire funcitong. 

This description can only do harm to you, your sister, and your family and no one else. Because these norms are such a huge epitaph of society, you can expect a huge backlash if you and your sister are ever found out. 

This backlash will hurt you and your sister, lead to incarceration if your state has deemed incest illegal, and even cause seer mental distress due to ostracisation by society.

So, if you and your sister are engaging in this form of relationship, It is an understanding that you must reach amongst yourselves considering you both know your family best and now know what kd of backlash you might get. 

What you can do is have a discussion with your sister about the situation, seek out professional help from a therapist or a sex therapist or a relationship therpaist, to help both you and her understand your situation more in depth. 

It is through developing insight that you and your sister can make a decision as to what both of you can do next regarding the relationship.

What is incest?

Incest refers to the sexual relations practised between individuals who share a direct blood relationship, such as between siblings, parents and children, grandparents and descendants, or whatever the biological or blood relationship between the two individuals.

Incest also extends to the cousins, although the greater their distance, the more loosely the relationship will be judged.

Incest as a phenomneon that is a culturally rejected and forbidden in almost all civilizations, since exogamy (sexual relations with individuals outside the family group) is preferred to inbreeding as a way of species survival by those that came before us. 

While there has been many hisotrical figures and cultures that has engaged in incest with no dire consequeses other than the genetic diseases that had costed them their lineage sch as the ancient egyptians, as of today it is considered a morally challenging phenomenon.

How is incest viewed by society?

Incest is a culturally rejected and even persecuted practice, which in some countries is even illegal, while in others it is tolerated but without any right to legally consecrate the union through marriage.

In almost all religious codes it is viewed as an immoral, forbidden union and its often cursed offspring. 

The rejection of incest can be understood as a result of human being’s preferences of exogamny over inbreeding as a way to help the species survive and flourish. 

Given that individuals belonging to the same family share a high percentage of their genetic material, incest was considered a union that impoverishes and reduces the genetic variability available for future generations, thus increasing the incidence of hereditary diseases and defects. 

Thus, the preference of exogamy. This particular preference must have been made by observation which then became a cultural custom that later became a question of morality as religious text and beliefs were developed. 

Why does incest occur?

Here are possible explanation and theories surrounding the question of why incest occurs:

  • Psychoanalytic explanation of incest by Sigmun Freud understands incest as a result of a primitve human’s need for reproduction. 

That incest was a result of the confrontation of men for access to the reproduction. That within a human hord that has limited availability of a female mate that is not biologically related might have led men to copulate their siblings as well as their parents to ensure survivability. 

However, it was hypothesised that the practice would have received all that burden of anguish, disease, and genetic diseases that would ultimately lead to the practice being despised, abandoned and replaced by exogamy.

  • Social explanation of incest

Considering that we are a gregarious species, that is, that tends to constitute groups, it is natural for a family nucleus to seek to expand its economic, political or social capacity by uniting rival clans through exogamous marriage, instead of withdrawing into itself with the inbred.

This was seen in the case of Royal ancient egyptions , who in a bid to keep power within the family reported to incest to keep the bloodline “pure”.

  • Family dysfunction

In recent studies of family functioning, incest has been understood as a result of family dysfunction. Disturbed family relationships lead to a shift in roles and expectations that can lead to children taking on the role of parents leading to incest. 

One particular example is the fictional story of “Flowers in the attic” where the older siblings take on the role of parents and engage in incest. 

Dysfucntional couples where there is a lack of spousal sexual activity is a common preceding factor to incest. Oftentimes, the destruction or dysfuntion of the family is present before incest occurs.

What are the consequences of Incest?

The consequences of incest are mainly based on social rejection, the emotional or psychological problems they may produce, such as feelings of guilt, etc.

If the relationship between the siblings is non-consensual, there are expectations of psychological distress in the victim. 

It has been observed that most of these sibling incest relationships have one sibling that is 4 years younger and considered the victim who has been groomed by the older sibling. 

The victim in these cases experience negative consequences such as somatic problems, depression, nightmares and anxiety, and depression.

In the case of relations with offspring where it is consensual and there is an offspring involved, there is a risk of mutations and diseases related to it. 

Some of the genetic diseases and medical complications that can arise include:

  • Down syndrome and other delays. Although this is not the only and exclusive cause of mental retardation, a higher rate of this type of disease has been seen in the offspring of very genetically close individuals.
  • Malformations. Similarly, children born with deformations or with dysfunctional bodies are often the result of incest.
  • Hemophilia. This disease that prevents or hinders the correct blood coagulation has been known as “the disease of the kings” because it was frequent among Spanish kings descendants of noble houses of marked inbreeding tendency.
  • Harlequin disease. Called Harlequin Ichthyosis, it is a very rare genetic skin disease that resembles a harlequin costume in newborns: thick, large scales from around the body and are born with the red-eyed, inverted eyelids.

Other than these medical conditions, a person who is in an incestual relationship can struggle with guilt, shame, and face social ostracisation and even persecution if incest is considered illegal in their state.


In this blog post, we answered whether having a physical relationship with one’s sister is wrong. We defined the term incest and point out the biological, psychoanalytic, demographic explanations of incest.


I am in love with my sister. Times of India. Retrieved on 3rd Dec, 2021.

Lande RG. Incest. Its causes and repercussions. Postgrad Med. 1989 Jun;85(8):81-6, 89, 92. doi: 10.1080/00325481.1989.11700738. PMID: 2726650.

Jarošová, L. & Weiss, P.. (2007). Sibling incest and it’s consequences. Ceska a Slovenska Psychiatrie. 103. 220-224.

FAQ about having a physical relationship with sister

Is it normal to be attracted to family members?

It is not normal to be attracted to family members, however, there are enough cases out there to prove that this happens.

There is even a term for this, called Genetic Sexual Attraction, or GSA.

Why don’t we find our siblings attractive?

We do not find our siblings attractive because we grew up too close to them.

The constant closeness leads to saturation of stimuli and too much familiarity between brother and sister, which kills any attraction.

This can be seen even in people who are not relatives, but who grow up in the same house.

What is it called when you are attracted to your sibling?

When you are attracted to your sibling, you may speak of Genetic sexual attraction.

GSA means that a strong sexual attraction may develop between close blood relatives, but only when the two first meet as adults.

In other cases, we speak about incest. 

Is it illegal to sleep with your cousin?

In most countries, yes it is illegal to sleep with your cousin, parent, grandparent, sibling. 

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