What is the relative of clam and oyster?

Clams and oysters belong to the phylum Mollusca, which also includes animals such as snails, squids, and octopuses. Within this phylum, both clams and oysters belong to the class Bivalvia, characterized by their bilaterally symmetrical shells that are composed of two hinged halves, or valves. As such, clams and oysters can be considered close relatives, with other members of the Bivalvia class being their closest relatives.