Is it best if parents have two children instead of just one?

Asked by msh (4270) January 6th, 2016 from iPhone

I have friends who have had just one child. I have others whom have had two or more offspring. The question comes up in my mind when they start egging each other on about their choices. One child families, in a positive situation, would have two parents who give their child their undivided attention. One Dad even says that it is easier to write a will because the one child inherits all of their money, possessions, etc. Multiple children parent’s argument is that if something happens to them, the children have each other- again, in ideal circumstances. If one needs medical help, or a place to get back on their feet again, a sibling is there for them.
Where do you stand on this issue? One child, two, three? More?
Are the rationale of their choices sound?
Does it really make a difference?