No, we didn't see those early memories with Jock and his sons or Miss Ellie, but you have to wonder.. If Wes was really Jock, surely some of those would have come up, at least off camera. Bobby and J.R. were never convinced for a second that Wes was Jock. If any of those things came up that only Jock would know, it seems Bobby and J.R. would have at least had some question. Unless, we were expected to believe that Jock rambled off his whole life story when he had that fever.
There are things, details as parents raising children that a parent wouldn't forget. Perhaps that's part of the reason J.R. and Bobby never bought it. I guess for me, that, and the fact that you would think Miss Ellie would somehow know a man she was married to for what, nearly 50 years, make it seem very unlikely that he could have been Jock.
It was a fun plot, and the writers did a good job of making us wonder, based on what we had experienced with the Jock character. However, I don't think Jock would have considered selling Ewing oil to anyone, let alone Jeremy Wendell.