Grandpa is sitting in front of a transition of some kind.
The top photo has brick patterns for the sidewalk. If you look to the left of Grandpa's feet, there is a solid concrete partition separating the brick sidewalk from whatever is underneath the bench (I can see it more clearly in the version I have open in Photoshop.)
And the wall on the top photo is not the same as either wall behind Barack and family. The wall to the left of Grandpa transitions to something slightly different behind his back. In the photo I have there is a distinct difference in the construction of the wall to the left of Grandpa and to his right. But neither match the exact style of construction of your top photo.
I think yours is the only possible explanation other than photo shop ....but my gut tells me this is the bench or the same type of bench and the wall....
If it is the same type of bench the bench in the Obama pic is distorted and if it is the same wall just a different location .I think the pattern on the vertical joints will be consistent and unlike that in the Obama pic