Final answer:
The probability of individuals in the third generation expressing the disorder depends on their genotypes. If both parents are carriers of the disorder, there is a 25% chance their children will express the disorder.
Step-by-step explanation:
In the pedigree, individuals with the disorder are indicated in blue and have the genotype aa.
Unaffected individuals are indicated in yellow.
From the information provided, we can determine that individuals in the third generation (iii) will express the disorder if they inherit two recessive alleles, indicated by the genotype aa.
Therefore, the probability of individuals in the third generation expressing the disorder would depend on the genotypes of their parents.
If both parents in the third generation are carriers of the disorder, there would be a 1 in 4 (25%) chance of their children expressing the disorder.