blood brother:
(plural: ‘blood brothers‘)
two boys swearing to be blood brothers
a person of a group of men who have taken an oath or made a solemn promise to treat each other as brothers and help each other, during a ceremony in which their blood, usually making a cut in the hands or fingers of two of the group and pressing both cuts together so that blood from both wounds is mixed to become one;
a man or boy born to a person’s own parents — your own brother (i.e. not a step-brother or cousin),
a member of a group taking care of her wounded blood brother
I warn you not to mess with Harry; he has a very powerful blood brother.
Though Jeremy Watson and Leo Watson are blood brothers, they have nothing in common — Jeremy likes blondes but Leo likes redheads; Jeremy likes to study but Leo likes to act; and so on.
When we were young, all the boys in the neighbourhood swore to be blood brothers to one another, and fought with the boys from other places who came to play in the nearby park!
