What every parent should learn is that constantly pandering to the whims and cries of one of their kids will not only create an unhealthy sense of entitlement in that child, but will increase the likelihood of the other kids envying and turning against that sibling. In the end the children will grow up somewhat disunited and will be constantly looking for ways to gang up and antagonize that child, especially when the parents are away from home.
Also, there will be attempts by the other kids to copy the antics of the manipulative child. This usually leads to being spurned by the parents who are by now sick and tired and don't need another like the spoilt child they now have. This will cause bitterness and a sense of despondency in the copycat child.
So you end up having a spoilt child who will throw tantrums any time they don't get what they want, sulking ones who think "why not me" and other brooding children just laying in wait to teach the special one a lesson.
And, yes, I am going somewhere with this...think about it.