When I first watched the episode Sarek, I actually thought the son whose wedding Picard attended in the past was another son (other than Spock). I thought perhaps Perrin had a child with him.
One of the reasons for this, when Sarek and Picard mindmeld so Sarek can draw on Picard's emotional control. Picard as Sarek, says "Amanda, Spock did you know how much I loved you"? It was almost like he was talking about both of them in the past tense. Of course 2 seasons later, we find out Spock is alive, but estranged from his father (again).