Board Thread:Series general discussion/@comment-24760042-20150719150828/@comment-26160856-20150719154740

Darby said on Twitter that the reason Clay said "....The Sun, your Son" is that when Juno showed the future about The Earth, Lucy and Desmond, she also showed him some "Alternate Realities" and in one of them, Desmond had a child. So in that moment, Clay was fighting to remember which  reality was the "Real one"