A set of identical, or once-identical, genes, derived from a single parent gene; need not be on the same chromosomes; classic example is the globin family in vertebrates.
A gene family is a set of genes defined by presumed homology, i.e. evidence that the genes evolved from a common ancestral gene. They generally share some biochemical activity. Genes are generally categorized into families based upon shared sequence motifs and similarities in structure.
Group of closely related genes that make similar products.Two or more genes that are related by divergent evolution from a common ancestor, either by speciation or gene duplication.