Do Siblings Have the Same Blood Type? Simplified Answer

| Reviewed By Amanda Lundberg, BSN, RN

At a very early age, siblings begin to share without even realizing it. As stated in a source about sibling relationships, they share about half of their genetic makeup. Despite similarities among siblings, there are also inherent differences due to their genetic makeup.

Do siblings have the same blood type? Siblings do not necessarily share the same blood type. Like other traits, blood types are inherited from parents. Parents with the same blood type are more likely to have children with the same blood type. If parents have different blood types, the children have many more blood type possibilities.

What determines blood type? Why does it matter? Let’s find out.

Blood Type Among Siblings

Full biological siblings generally share 33% – 50% of their DNA. DNA is not passed on in a single block from generation to generation. Everyone has an ABO blood type (A, B, AB, O) and an RH factor (positive or negative). 

Which Parent Determines the Blood Type of the Child?

Maternal and paternal genotypes determine what type of blood children and siblings will have. Blood types are inherited and represent genetic markers of both parents.

Each parent donates one of two ABO genes to their child in addition to one RH factor. The RH factor is a protein that covers your red blood cells. If the protein is present, you are RH Positive. If the protein is absent, you are RH Negative.  

What Determines Blood Type?

Parental genes will determine children’s blood types. Which ABO and RH Factor blood genes are passed on to children depends on if the genes are dominant or recessive.

A and B genes are dominant. O genes are recessive. RH-positive is dominant. RH-negative is recessive. These genetic donations and pairs will combine to determine the blood type of your child(ren).

Examine the table found in BYJUS study materials. The table displays gene dominance patterns. Children’s blood types are a combination of parental genetic contributions. Physiological traits are not identical.

Recessive and dominant genes allow for genetic differences not only from parent to child but from sibling to sibling. 

Do Most Siblings Have Different Blood Types?

Children will inherit randomly selected DNA from their parents, which could be the same or very different from their siblings.

There are four maternal blood types and four paternal blood types, which leaves 16 combinations to keep in mind when predicting a child’s blood type.

Sibling blood types rest solely on the blood types of the parents, not other siblings. If the parents have the same blood type, there is a higher probability that the siblings will have the same type as well. 

Do Twins Have the Same Blood Type?

Identical twins have the same blood type. Fraternal twins may or may not have the same blood type. 

Does Blood Type Matter?

Blood type is a factor that can contribute to health risks. Blood type matters when donating/receiving blood and for organ transplants.

Blood type during pregnancy is crucial information. If a woman is RH-negative, it can cause complications for future pregnancies due to a buildup of antigens. 

How Many Blood Types Are There?

There are four main blood types: A, B, AB, and O. Each blood type can be either RH positive or RH negative, resulting in a total of eight blood groups. 

What Is the Best Blood Type?

Type O blood is considered the most versatile. O-negative blood type is known as the universal blood type because it is safe for everyone to receive O-negative cells.

O-positive blood type can be donated and received by all other positive blood types. It is the most used and the most needed blood type. O blood types are also associated with longevity due to a lower risk of cardiovascular disease. 

What Are the Different Blood Types?

There are eight different blood types: Four blood groups and two RH factors

  • A + 
  • A –
  • B+
  • B – 
  • O +
  • O – 
  • AB +
  • AB – 

What Is the Most Common Blood Type?

O-positive is the most common blood type. Approximately 37% of the world’s population carries O-positive blood. 

What Is the Rarest Blood Type?

The rarest of the 8 basic blood types is AB-.

The world’s rarest blood, known as “Golden Blood,” is RH-null, which contains no RH antigens. Fewer than 50 cases have occurred worldwide.

Who Can Donate Blood To Whom?

Blood Type Donate To 
A+A+, AB+ 
A- A+, A-, AB+, AB-
B+B+, AB+
B-B+, B-, AB+, AB-
AB+AB+
AB-AB+, AB-
O+O+, A+, B+, AB+
O-Everyone

You can find more information on blood donation here.

Related Questions:

Do Family Members Have the Same Blood Type?

No, not all family members have the same blood type. It is common for family members to have various blood types. 

Does Blood Type Affect Personality?

There is currently no scientific evidence suggesting a link between blood type and personality.

Interestingly though, there is a widely accepted Japanese theory called Ketsueki-Gata, which seeks to link personality traits as a result of physiological factors, such as blood types. 

Final Thoughts

Siblings may or may not have the same blood type, but nonetheless, they are each a unique blend of their parents.

Siblings who share a blood type may not share any interests or mannerisms, while others may share similar personalities without any substantial physiological similarities.

A sibling is a child’s first best friend and life’s greatest companion.