The Psychological Differences Between Brothers
In principle it is shocking that siblings differ so much psychologically when it is assumed that the personality is strongly determined by genetic factors.
How can it be understood that even single twins raised in the same family environment end up being psychologically so different?
Statistically, it is more frequent that siblings have different psychological characteristics instead of related profiles and it is usual that these differences are very marked
Some theories suppose that the brothers establish systematic rivalries to be object of attention, to obtain more resources and to gain status in the family hierarchy and that forces them to differentiate themselves psychologically.
It may be that way judging by the permanent transcultural presence of fraternal rivalry that in the case of psychoanalysis also extends to the father himself.
In the absence of unequivocal empirical confirmation, in general, it has been accepted that psychological differences between siblings are determined by the order of birth, sex, family size and age difference.
In popular culture, the disorder of birth has always been considered as a determining factor of the way of being:
The firstborn are more responsible and smarter.
The only children are more egocentric and more capricious.
The Benjamins are more spoiled and more astute as children's stories point out.
It is not clear that the order of birth alone explains the psychological differences between siblings but surely helps to confirm the strategies and learning of each of them.
It seems that the variable sex is the most important to decide the psychological differences between siblings. Since it intervenes directly in the brain organization and promotes different generic learning, but we must not underestimate the weight of the other two variables (the size of the family and the difference in age between siblings), which has been gradually reduced in most of the reproductive patterns of a particular culture.