Originally Posted by ijgordon

In this situation, if 3B doesn't want to move (for whatever reason, maybe they sleep on their right side and like to face the aisle), then you still have the opportunity to ask 3F to move over to 3A and you and the Mrs. can have 3E/F.
It would be unusual for BOTH passengers to refuse a like-for-like seat, just on the opposite side of the aisle, but maybe 3A really likes being on the North side of the plane where it's usually darker for longer....