The only circumstance under which two people will share a genotype is when those two people are

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Monozygotic twins, also known as identical twins, develop from a single fertilized egg and therefore have the same genotype. Biological siblings may share some but not all of their genotype depending on how genes are passed down from their parents. Step-siblings may share some genotype depending on whether they have the same biological parent. Dizygotic twins, also known as fraternal twins, develop from two separate eggs fertilized by two separate sperm and are no more genetically similar than any other pair of siblings.

The Only Circumstance Under Which Two People Will Share a Genotype