Now David was old and full of days; and he made Solomon his son king over Israel.
"Now David was old ... and made Solomon his son king over Israel"  (1 Chronicles 23:1).  The truth here makes it impossible to receive Nathan's prophecy in  2 Samuel 7 as a primary reference to Solomon.  The Great One mentioned there was prophesied to be born after David slept with his fathers.  This verse clearly indicates that Solomon enjoyed a co-regency for an unspecified time with David his father.