This has been a complex topic for so many people, so it’s important to simplify it here—separately from family vocabulary: simple to complex names to call your relatives. In all ramifications, these concepts are different and are in no way synonymous.
Relax, you will definitely understand them perfectly with this simple analysis:
If your mum remarries and gives birth to a child, the child is your half-brother or half-sister because the person who gave birth to you gives birth to him or her. Likewise, if your father remarries, the child he has through the new wife is your half-brother or half-sister because the child is your father’s.
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