In my previous post, Presidential family portraits, I tried to make a comprehensive analysis of the presidential portraits through the centuries. I should add that my critiques of the paintings and photographers are mostly cultural rather than aesthetic. Even the family sprawl of the Kennedys is endearing. Except when it comes to the Obamas, whose family portraits I really find odd and off-putting, with all the clutching that is going on.
But to describe a little more the aesthetic decisions in the portraits:
The perching on the arms of chairs (in the Truman family portrait and the Nixon family portrait) I think are aesthetic choices by the artists. In the Truman portrait, a type of pleasing triangular structure is formed, with Margaret appearing higher (standing would make her too high) to form the triangle. This is a common portrait strategy, which I describe here. This triangular form is somewhat used in the the Roosevelt photograph.
Framing the image is another common strategy, which is evident in the Nixon family portraits. In the top one, the older daughter and the mother frame the photograph. In the later portrait, David Eisenhower sits beside his wife Julie Nixon, perched on the sofa arm, (yes, the photo does attempt casualness), while Patricia Nixon completes the frame on the other side of the sofa. There is also an attempt at symmetry, with President Nixon flanked by his (colorfully dressed) wife and daughter.
But, I wasn't trying to revisit these portraits. As I was looking through the many images out there of the Obama children, I was struck by the masculine, flat expression on Malia's face in recent photos (2011 especially). She used to look pretty as a little girl. It seems that some of her mother's empty harshness, and her father's arrogant air has rubbed on to her.