Homework problem:Introductory genetics
Ok, Josh has PCD. That gives three possible genotypes for parents:- ( let the alleles be P and p)

1) Pp x Pp
2) Pp x pp
3) pp x pp

In (1), the probability for next child to be pp is 25% and to have the disease is 12.5%. 

In (2) and (3), the probability of any parent to be pp is rare as the p allele is quite rare (discussions with swbarnes2 in comments). So the real probability will be only slightly higher than that of case 1 i.e. 12.5%