This was also a big discovery for me after I left home at 18. While I was growing up it was all about the differences between the siblings - me argumentative and inquisitive, my brother mathematical and reserved, my sister empathic and gentle, my other brother funny and aggressive. Then after you have left home you realise that these are people with whom you have a massive shared set of values and experiences which outweigh the differences between you. And after years of going outwards, you turn back towards them, and appreciate them more. That's how it has been for me anyway.
I read the other day that having four children or more was associated with stress (no!) and unhappiness. I do believe my parents had a very difficult time raising us all with very little money, and if they were often difficult to be with, in retrospect I can understand why. But for me, having three siblings is great. I just wouldn't inflict that level of fecundity on myself.
