I read many weeks ago that at about age 6 is the age where kids develop a sense of themselves by comparing to others, and hence the "not fair" begins. This is absolutely true about Big M. If he doesn't get something he asks for he says, "but it's not fair that [so and so] got one". "Not fair" has become so much a part of his everyday language that his sisters, who are a few months shy of 5 years old, and his almost 2-year old brother are now saying it too.
Can you imagine having to explain and justify your parenting decision to a 7 year old? I'm sure this is somehow a segue into teen-hood and I have 4 going through it at the same time. Four children is a chore, and having twins in the middle adds it's unique challenges.
Welcome to parenthood, where "the days are long, but the years are short". (Thanks to the Minivan MacGyver for the quote.)