One of my ESL students once asked me the difference between a stepbrother and a half-brother. After explaining it to her, I realized that many international students of English struggle with these two words. Its probably because in quite a few languages there is no distinction between a step and a half-sibling. There is usually just only one word for both.
So, what is the difference between a stepbrother and a half-brother?
A half-brother is someone who shares only one parent with you; either his mother or his father is your biological parent as well. Hence the term half-brother. A stepbrother, on the other hand, has no blood connection with either of your biological parents.
So, in a nutshell, a stepbrother has no blood connection with you, but a half-brother shares your bloodline with only one of your two parents. He is the child of your stepmother or stepfather from his or her previous relationship. The same distinction applies to your stepsister and your half-sister
An example of a half-brother is when your parents separate, and your father remarries. If he has a son with his new wife, he is your half-brother. In the same way, your mother could have a child with a new husband – this would also be your half-brother.
Now if your father’s new wife (your stepmother) also has a son from her previous marriage, then he’ll be your stepbrother because you don’t have any blood connection with your father’s new wife.
Another example of a stepbrother could be an adopted son of your parents. So, for instance, if your parents adopted a child before they conceived you, will also make him your stepbrother, because there is no blood connection.
There are some nuances between the half-brothers or half-sisters. If you share a common biological father, then he/she will be your paternal half-sibling. Similarly, if you share a common biological mother, then he/she will be your maternal half brother or sister.
A foster brother is a yet another nuance that brings a bit of complexity to the step-sibling relationships. Technically speaking, a foster brother/sister is a child that was raised by your parents for some time but was neither their biological child nor legally adopted. The fact the child was raised in the family makes him your foster brother. Sometimes orphan kids are raised together as a family unit by some philanthropic organizations like an SOS Village. Kids raised in these kinds of foster homes are called foster brothers or sisters.
A stepbrother can even get married to his stepsister and have children since no biological relationship implies that their descendants may have genetic problems in the long run. Yes, the societies may not accept these marriages, but only morally, since having different parents, stepbrothers do not share genetics, and their relationship would be the same, in these terms, as one with someone outside the family.
To sum up, whenever you hear the word ‘step,’ it means a person has to step into the role of someone else. Because it’s not a biological relationship, therefore, it’s not a blood relationship. A stepfather, a stepmother, a stepbrother or a sister are all social relationships without common genes. A half-brother or a half-sister, unlike step-siblings, share common genes from either a mother or a father. The picture above visually explains the difference clearly. The embedded YouTube video explains it further with an example.