alt Hacker NewsI’m a twin - admittedly boy/girl, so already with some fundamental differences - and we are very, very different people. Always have been. Different interests, different ways of seeing the world, different attitudes to competition, sports, social relationships etc.
Now I’ve got 2 boys, and even at fairly young ages they were very different. I’d say by 6 months old the basics of their personalities were visible, and they haven’t changed vastly as they’ve grown.
The twins I have known are the same. I would assume it has something to do with a desire to differentiate themselves from one another, but they always seemed far more dissimilar in personality and affect than my siblings.