Blood and milk brother

• blood and milk brother: reference to Eoin MacNeill: Celtic Ireland, 55: 'Lugaid Cichech... reared the two sons of Crimthann, Aed and Laegaire, on his breasts. It was new milk he gave from his breast to Laegaire, and blood he gave to Aed. Each of them took after his nurture, the race of Aed being marked by fierceness in arms, the race of Laegaire by thrift'
• blood brother: two males related by birth, or two or more men not related by birth who have sworn loyalty to each other (often by ceremonial mingling of blood)
• milk brother: two males that are breast fed by the same woman (or foster brother)
  • a blood and milk brother would most likely be a twin