Deoxyribonucleic Acid or DNA is the genetic material present in all living organisms.
It is a double-stranded helical structure composed of a backbone of pentose sugar and phosphate group with four nitrogen base pairs adenine, guanine, thymine and cytosine.
All the genetic information of an organism is present in the DNA which is passed on to each generation because it is hereditary.
Siblings
Siblings always have different DNA with only about 50% of it matching with each other.
This variation is due to the fact that during the formation of gametes each cell goes through recombination of DNA.
This leads to the production of haploid gametes that are non-identical to each other and only have half of their parent's genetic content.
After fertilization, both the maternal and paternal DNA combines to give rise to the diploid individual which shares not more than 50% of the similarity with their parents and each other.
So every individual that is born except for identical twins has a very unique genetic makeup.