Big Brother, by Lionel Shriver.

When Lionel Shriver (I love Lionel Shriver!) calls him “big brother,” she means it in both senses of the phrase (older and obese).  Little sister Pandora is surprised and horrified when Edison is wheel-chaired off the plane and in the two months he’s a houseguest, his metamorphosis is like the elephant in the room.  (The denouement (jeez,…