Pedigrees are used to help geneticists understand how traits are inherited between generations. The romanovs, a russian royal family, had a history of hemophilia, a sex-linked disorder that is determined by a recessive allele on the x chromosome. What is the best evidence to prove that irene was heterozygous for hemophilia? elizabeth is not a carrier for the trait. Tatiana carried the recessive allele. Her brother has hemophilia and her sister is a carrier. Two of her sons have hemophilia and one does not.