I will try to answer in English...I live in Belgium. I'm 22 and we are with 3 sisters in our family. So we have to shra everything all the time! I think it is important to learn that.
for example: if I had a biscuit, I must always give a part to my 2 sisters, so we broke the biscuit in three parts.
i work a lot with young children and sometimes I meet kids who never want to give a part to their friends. I think that one of the reasons is that they never done it before. So learn your cld to share, even when it have no brothers or sisters!
Bye
I think you'll have to undergo a systematic review of the literature, and you can find helpful citations in the Social Sciences Citation Index and the National Library of Medicine (PubMed).