Research Papers / Siblings vs only child: Early Childhood studies [5]

I am doing a specail study on Siblings vs only child.
the focus q's are
1.DO CHILDREN BENEFIT IN AREAS OF EMOTIONAL AND SOCIAL DEVELOPMENT COMPARED TO THAT OF AN ONLY CHILD
2.WHAT SOCIAL BENEFITS ARE GAINED FROM SIBLING RELATIONSHIPS?
3.ARE LEVELS OF EMPATHY HEIGHTENED FROM SIBLING RELATIONSHIPS?
4.DOES THIS DEBATE BECOME NULL AND VOID ONCE AN ONLY CHILD STARTS CHILDCARE AND/OR SCHOOL?

Any input into this topic would be much appreciated..
Thanks..=D