Dreadful Parenting

Recently, on a delayed trans-atlantic flight that had me cornered at the back of the plane with no less than three families of young children, I had a chance to observe differing parenting skills.  The very young children in my immediate seating vicinity were all approximately the same ages (each family had two, about 14 months and about 3 years).  Two sets of kids were wonderful.  One set was not.  What was the difference?

I had ample time to think about this as the 3 year old boy sang show tune