There are many degrees of kinship in the world, blood and acquired, which are sometimes difficult to understand. This also applies to the concept of "brother", because brothers are half-blood, half-cousins, half-cousins, cousins / second cousins, named.
Step-brother
When a man or woman with children remarries, the new partner may also have children from the previous marriage. In this case, their children will be half-brothers and sisters. Thus, a half-brother is the son of a stepmother or stepfather; he is not a biological relative. Stepbrothers (and sisters) do not have common parents, although they live in the same family, i.e. are "brought together" in one family.
This situation is socially and legally classified as a non-blood relationship. At the same time, half-brothers and sisters can become blood relatives through their descendants. This is possible if the wife and husband, who have children from previous marriages (stepbrothers / sisters), will have common children, who will be half-and-half for the older children. The descendants of both those and others will be consanguineous.
Often brothers / sisters who have a common father (half-blood) or a common mother (half-uterine) are called step-by-step brothers / sisters.
Named brother
The named (or named) brother, unlike the half-brother, is not even a formal relative. He is not native by blood, but dear in mental and emotional terms. This is usually a close friend with whom a lot has been experienced, with whom there is a lot in common and on whom you can rely. When people call each other named brothers, it speaks of deep friendship and trust between them.
In Russian folk tales, the named brother is the one who swore an oath to be someone's brother, i.e. "Called himself brother", fraternized. The word "named" has synonyms - twinned, twinned, which were more widely used in the past.
Also, in ancient times, there was a practice of exchanging body crosses between close friends. Such people were called crusades or, again, named brothers. The relationship between them was called a crusade or twinning, which implied clear norms of behavior and voluntary obligations of mutual assistance. The Russian epic "Fight of Dobrynya with Ilya Muromets" describes the duel between the heroes Ilya Muromets and Dobrynya Nikitich, after which they, formerly worthy rivals, become twin brothers, crusaders. At the same time, Ilya Muromets, the oldest and the winner in the duel, becomes a big brother, and Dobrynya - a smaller one.
The second meaning of the word "named" is a step-son (or daughter), and for the natural children of the parents who adopted another's child, he is a named brother. This meaning of the word is considered obsolete.
