Genes - Why are Brothers different? This question might seem childish but i still don't understand it. Why are two Brothers different. Children get 23 chromosomes from their father, and 23 chromosomes from their mother. So each child has 46 chromosomes, 23 pairs, half from the mother and half from the father. So why aren't brothers identical? After all, each male child should have 23 chromosomes from his father and 23 from his mother? So what makes brothers different from each other? If i DNA test two brothers, would they not have exactly the same 46 chromosomes? John.