The congenital analgesia

Congenital analgesia is a rare disease in which the patient’s body is unable to perceive and respond to pain. This genetic disease is controlled by recessive genes. We use ‘P’ to represent the normal allele, ‘p’ represents the disease allele. Individuals with ‘PP’ and ‘Pp’ genotypes are phenotypically normal, while individuals with ‘pp’ genotype is diseased. A married couple, in which the mother is heterozygous with a genotype ‘Pp’ and the father is diseased (pp), is planning to have five children.

What is the probability their first two children will be diseased but the third child will be normal?