The phrase "normal littermates" refers to the typical or average brothers or sisters born from the same mother and father at the same time. Full definition
In some ways, genetically normal littermates behave like mice that carry an autism - related mutation, despite not having the mutation themselves, scientists report. (sciencenews.org)
Dwarf pups are indistinguishable from normal littermates up to 2 mo old. (merckvetmanual.com)
PCR amplicons from COLQ exon 14 are 470 bp in size and cleaved into 204 and 266 bp fragments in the presence of c. 1010T > C. Three clinically normal littermates were identified as carriers, denoted by semi-filled icons. (journals.plos.org)