If a man and a woman, each with sickle-cell trait, were planning to marry, what information could you provide them regarding the genotypes and phenotypes of their future children

I'll inform them that the possibility of all their future children/offspring being phenotypically sickle-celled is very high.

Explanation:

Sickle cell is an inherited disease condition in which the red blood cells of the blood loses its shape and hence, dies or gets broken down. It has to do with the blood genotype of an individual. There are three major types of blood genotypes in humans namely: AA, AS, and SS. SS is the recessive genotype that codes for the sickle cell trait.

Hence, a human with the sickle cell trait has a genotype- SS. Therefore, according to this question, a man and a woman, each with sickle-cell trait (SS), were planning to marry, This will mean that both the man and the woman will always produce a gamete with S allele, which will combine to form an SS offspring. In other words, all of the offsprings of this man and woman will be sickle-celled.