J.C.
I think most responsible parents wonder how having a second child will affect their first child. Just because your friends are not parenting well and balancing their energy on both children does not mean that you will do the same thing.
My children are 2.5 years apart and they love each other. My daughter has no shortage of attention and love and they have to share and be kind to one another because that is what I have taught them.
It is a balance act to be fair and equal with your love and one one one time with your children, but a good parent, who does not treat one child as the golden child, will be able to raise two, well adjusted, loved children who are kind and loving to one another.