How many future children of the affected individual will be carriers?

PKU (phenylketonuria) is an enzyme deficiency disease that only develops in individuals who are homozygous recessive for that gene. An individual with PKU has parents that do not have this disease. What is the parents’ genotype for the gene responsible for PKU? What is the probability that they may have another child with PKU? How many future children of the affected individual will be carriers? Explain your answers.