How common is it for step siblings to marry?

In this blog we will discuss how common it is for step siblings to marry. 

We will also briefly discuss whether it is illegal to marry step-siblings, what are the laws that prohibit step-sibling union and also why step-sibling attraction occurs. 

How common is it for step siblings to marry?

It is not very common for step siblings to marry however there is no official research that gives an estimate about how common it is for step siblings to marry. 

However, writers at Family law attorneys estimate that sexuality between step-siblings is rare but it does happen. Due to lack of research and statistical estimates, it is not possible to give a number of how common it is nor of it’s prevalence. 

However, reseachers suspect that sexual and romantic relaitonships between step-siblings does occur however, lack fo research chould be because of the taboo surrounding incestual relationships including relationships bewettn non-biological siblings due to the bond created by the institution of marriage shared by the parents of step siblings. 

While step-siblings are not connected by blood, it is still frowned upon because when their parents marry they are considered a family as a whole, which makes it unacceptable that two “siblings’ ‘ develop a romantic relationship with the desire to marry. 

When it comes to getting married as step siblings, it is not as simple as the legal and cultural ban on insectual marriages or unions. 

When it comes to incestual relationships between two siblings or other family members it is considered illegal in most cases and is frowned upon in most if not all modern societies.

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 legal recognition of the union through marriage.

In almost all religious codes it is viewed as an immoral, forbidden union and it often curses the 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- as a result of biological and social concerns. 

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. 

However, in the case of step siblings, the threat of biological consequences is not urgent; rather, the rejection of such relationships arises based on how society will view the people involved- that is, the parents of the step siblings, the peers, extended family members, co-workers etc. 

In most counties and cultural societies, even if you are step siblings with no biological connection to each other, it is generally frowned upon and this might impact the marital union of two step siblings where they might not disclose their relationship to each other making it difficult for accurate data collection regarding prevalence. 

Is it illegal to marry your step sibling?

While one might think that it is possible that one can marry step siblings because there is no biological connection between the two siblings, this could be a mistaken assumption. 

Incest laws of some countries include prohibitions in the case there is incenstual relationships between biologically-unrelated individuals, especially where they are legally bunded together as family as in the case of adoption and step-siblings. 

This is because most laws make no provision for the rare case of marriage between two people who have a lower degree or percentage of shared DNA.

The laws regarding incestuous realtionships in most countires is clear- most countries deem icest illegal. However, the law surrounding step sibling marital unions is not as clear. 

In the UK and the US, since step-siblings are not biologically related, it is most probably the case that your state laws will permit your union provided that there is consent from both individuals involved and authorization from the court and from other family members.

In some societies, there might also be a need to get the consent and permission from religious leaders, social leaders, or the head of the family for the union. All of this has to do with social acceptance of unions related to step siblings. 

The legality of whether you can marry your step sibling also depends on:

  • The nature of the family relationship of the parties involved which means that there should either be no biological connection between the two people involved or that their genetic connection should be less than 25 percent. 
  • Age of the parties where both parties should be consenting adults.

It is these factors that play into account whether the union is legal or illegal and also counts for the severity of the punishment that is dealt to perpetrators of the crime as well as whether conviction is passable in these cases. 

Now, another important factor that plays a role in the conditions that surround the legality of relationships between two family members is the degree of relationship between the people- usually looking into the degree or percentage of shared DNA. 

This particular degree of relationship is calculated by counting the number of generations back to a common ancestor. 

Most laws prohibit incestual relationships that are of 25% shared DNA or higher. These includes relationships such as:

  • identical twins; 
  • Parent-offspring
  • full siblings
  • 3/4-siblings or sibling-cousins
  • grandparent-grandchild
  • half-siblings
  • aunt/uncle-nephew/niece
  • double first cousins

Is there a law against step-sibling marriages?

In the US, there is no law that prohibits or is against the marital relationship between two consenting adults who are step-siblings. 

It is most probably the case that state laws will permit the union provided that there is consent from both adult individuals involved and authorization from the court and from other family members.

Within the UK, the marital union between adopted family members is legal only in some cases. A parent, even if they are not biologically related to the child, cannot legally marry their adopted or step child. 

However, adopted siblings with no biological relationships and step siblings with no biological relationships are permitted to marry by law. 

In some societies, there might also be a need to get the consent and permission from religious leaders, social leaders, or the head of the family for the union. All of this has to do with social acceptance of unions related to step siblings. 

Why does Step-sibling attraction occur?

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

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. 

It is possible that one of the causes that drives sibling incest is because the step-sibling develop a bond in the face of dysfunction and abuse from negelectful or abusive parents. 

No biological Taboo

Step siblings are not raised together nor do they have the biological natural taboo that keeps themagainst and away from sexual contact with each other because they have no shared DNA.

This lack of Shared DNA is the the cause of step sibling incest but it can make it more probably that this form of contact occur between two people who are step siblings.

Demand for closeness 

As the blended family gets together and there is an active encouragement by the parents and other adults for the children to become more close and share a familial bond, it is possible that this can take an unintended turn. 

The demand for closeness and affection between two individual, basically strangers, can  create an unspoken expectation that stepsiblings will move toward one another- ideally in a platonic and familiarly regard, 

However, it is possible that non-sexual advances can become secual and sexual implications can also develop in the case of most sexuallly developing teenagers who do not have a mature oposcyholgical boundaries and development. 

Developing teenagers

Another risk factors is developing sexuality fo teeagers who are steop siblings might lead to an obsession and curiosity about sex and sexual realtionshops. 

Changes in hromones and physical appearance inside a child’s body lead to many confusing thoughts and feelings for teenagers and when you mix this wiht underdeveloped moral and psychological development in teenagers, it is possible that it can lead to sexual interactions when the step children are left unsupervised.

Conclusion

In this blog we have discussed how common it is for step siblings to marry. 

We have also briefly discussed whether it is illegal to marry step-siblings, what are the laws that prohibit step-sibling union and also why step-sibling attraction occurs. 

FAQ related to How common is it for step siblings to marry?

What is a half sibling vs step-sibling?

A step-sibling, also known as a stepbrother or stepsister, is someone who is not related to you by blood but you are related to them by your parent’s marriage.

On the other hand, a half sibling is defined as siblings having a common mother or common father but not having the same biological father or mother respectively.

Is step-sibling relationship legal?

In the UK and the US, since step-siblings are not biologically related, it is most probably the case that your state laws will permit your union provided that there is consent from both individuals involved and authorization from the court and from other family members.

In some societies, there might also be a need to get the consent and permission from religious leaders, social leaders, or the head of the family for the union. All of this has to do with social acceptance of unions related to step siblings. 

Do step-siblings have the same blood?

No, siblings don’t necessarily have the same blood however they might share the same blood type but this does not mean that they are related by blood or have the same shared DNA.

Are step-siblings immediate family?

Yes, step siblings are included in the term “immediate family”.

What is it called when siblings sleep together?

When siblings have a sexual realtionships and sleep together, they have an incestual relationship which is considered illegal in most countries and is socially rejected and frowned upon.

How much DNA do you share with your half sibling vs step sibling?

Half siblings share 25 percent of their DNA where each sibling shares 25 percent with one respective parent that they are both biologically connected to whereas step siblings do not share any DNA. 

References

Is it Illegal for Step-Siblings to Marry? Find a Family Law Attorney. Retrieved on 14th March 2022.http://www.findafamilyattorney.com/Featured-News/2016/Is-it-Illegal-for-Step-Siblings-to-Marry-.aspx

Deal.R. What Do We Do Now? When Stepsiblings Have Sex. Smart Stepfamilies. Retrieved on 14th March 2022. https://www.smartstepfamilies.com/smart-help/learn/parenting-stepparenting/what-do-we-do-now-when-stepsiblings-have-sex

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