Draw a pedigree. Probability of 1st child to have sickle cell anemia?

The autosomal gene for sickle cell anemia (ss) is prevalent among East Africans. Affected individual shave elongated and curved erythrocytes under low oxygen tension because of the polymerization of hemoglobin. Supposing heterozygotes for this gene in this population occur in a frequency of 1 in 8. If a phenotypically normal guy marries a second wife who is also phenotypically normal, what is the probability of their first child to have sickle cell anemia? Draw a pedigree; write the genotypes of all persons involved in a Punnett square.