I guess that's possible. I just found it weird the kid would call him "Papa". Unless there's some kind of weird memory implanting thing going on, everything Ian knows comes from Cap, and I don't think Cap would tell the kid to refer to him as that, even if he is acting as a surrogate father figure to him.
Well, kids need parents, and since Cap is the only person he knows (only person not trying to kill/capture him he knows), and he's an older guy who is protecting him, he naturally identifies him as his Dad. Of course, I don't know where he learned the word "papa." So, I think that's your point--why is he calling him "Papa," of all things. I agree that I can't picture Cap telling him to call him that. Maybe it is a genetic memory or something strange like that.