He knows
In “A Call to Arms,” a second-season “Dallas” episode, Bobby (Patrick Duffy) notices John Ross (Josh Henderson) drinking alone in his bedroom and enters.
BOBBY: So that’s where the bourbon went?
JOHN ROSS: Sorry.
BOBBY: It’s all right. As long as you share. [Pours himself a glass, sits] So, how’d it go with Pamela?
JOHN ROSS: For once in my damn life, I told the truth. And she thought it was a move. I guess I’m the like boy who cried wolf. My reputation precedes me.
BOBBY: You know, J.R. always liked that saying of Mark Twain’s: “A lie can make it halfway around the world before the truth can put on its pants.” You spend your days lying and scheming, people have a tendency to be suspicious.
JOHN ROSS: I just can’t help but feel like I let her down.
BOBBY: Well [sips], if anyone in this house knows how complicated a relationship with a Barnes woman can be, it’s me. Whenever there was a conflict between me and my Pamela, she would choose her family and I would choose mine. As much as I loved her, I had to understand that she was a Barnes first, a Ewing, second.
Dallas Decoder 
I loved this scene! Patrick Duffy and Josh Henderson seem to have a great chemistry, just like with JR, Bobby knows that there is good in John Ross. I also couldn’t help but be reminded of a very early episode of the original series (“Secrets”, I think) when Miss Ellie explains that part of her will always be Ellie Southworth, despite the fact she had been a Ewing for so long. I am not sure if that was intentional but it really did strike me as wisdom being passed down from the generations.
Yes, great scene. Not only a great call-back to the original series, with Bobby reminiscing about his marriage to Pam, but it was a character-moment, a man give love advice to his nephew. It’s one of those universal scenes that everyone could relate to.
like that scene, my favorite scene starts with Sue Ellen saying Harris Ryland is on my find, and ends with JR3 saying your head’s going to look real nice above my fire place
But is Pamela really a Barnes first?
If you judge by the last meeting of Cliff and Afton I don’t know. Recall Cliff was very suspicious that Pamela was his but Afton was so distrustful of Cliff’s obsessive dark side that she hid Pamela’s parantage and claimed that drunk son of a Southern gentleman (the character name escapes me) was the father. The classic series ends with Cliff not definitively knowing the truth.
That makes me wonder, at what point in life did Pamela herself learn of her true father? We can only speculate right now but I’d bet on later than sooner. So I’d think Pamela would actually be a Cooper first.
The new series hasn’t filled in that background (just like they haven’t filled in a lot of what’s happened in the 20 years between the two series’), but we can make a guess. Last season, when Cliff first appeared, they said that Cliff and Christopher hadn’t seen each other in 5 years. And Christopher obviously didn’t know about Pamela, whom he’d been with for 2 years @ that point. So Cliff & Pamela somehow reconnected (either Cliff tracked her down, or Afton eventually told Pamela about her real father) sometime during that 3-year period between the last time Christopher saw Cliff and the time Christopher first met Pamela.
I think one could still argue the first meeting between Cliff and Pamela could be just before your theoretical five years ago but if so not by much. I guess I’d tend to agree with your guess JR LeMar.
So again if Pamela has only known her true father five years and she is certainly beyond a shadow of doubt seeing the true colors of the current Don Cliff now I’d argue this is where Bobby’s analogy breaks down. Pamela Rebecca is mostly likely NOT a Barnes whereas Bobby’s Pam was.
I enjoyed this scene. I think it is cool that John Ross and Bobby are starting to get along. Bobby wants to leverage the relationship between John Ross and Pamela Rebecca to the Ewing’s advantage. It is clear that Bobby also cares about John Ross and despite all of the B.S. that John Ross has shoveled. Bobby is uniquely positioned to really help John Ross out because he is his father’s brother and one of the very few people his father truly respected and also his marriage to the “Barnes girl.” This scene and the scene in the earlier episode where Bobby shakes John Ross’s hand and sincerely welcomes him home on South Fork, shows a new relationship between the two. I like it. I was getting tired of John Ross being such a jerk.