The parents are carriers of the disease, which means they both have the recessive allele but they don't have any symptoms.
Let's call the alleles F for the normal gene and f for Friedreich ataxia. Then the genotype of both parents would be Ff.
If we make a Punnett's square it would be as follows:
We can see that the couple can have non-carrier, carriers, and sick children, with the probability of having a carrier child being 50%.