col-lactānĕus (conl-), a [lacteo], a brother or sister nourished at the same breast, a foster-brother or sister (post-class.); masc., Gai Inst. 1, 39; Dig. 40, 2, 13; Inscr. Orell. 2281 al.; fem., Dig. 34, 4, 30, § 1 al.