Depending on what trait the alleles carry, the brothers will have a different phenotype and a different genotype. For example; Eye color. My sister is heterozygous, meaning she has brown eyes. I am homozygous recessive, meaning I have blue(green/hazel) eyes. We both have the same parents, I just happened to inherit both of the recessive eye color alleles from my parents whereas, my sister inherited both the dominant and recessive alleles.
So, since the brothers inherited different sets of alleles, their genotype for a certain trait will be different.
Cell have to spilt themselfs apart to make more cells for the system. Tree are like cells because they sometimes have seeds in them that help generations of trees grow!
