Here's the situation:
You and your spouse are talking with a third person who is of the opposite gender as yourself. e.g., my wife and I are talking with a woman named - let's call her Joan.
If I'm talking to Joan about my firstborn son, I don't want to say "my son" because it may imply that he is not also my wife's son. I also don't necessarily want to say "our son" because it may imply that Joan is the co-parent, even though everyone present knows that's not the case (it could be even more awkward with a couple talking to a man, and the wife is talking, because there might be a little more doubt about the biological parentage in that circumstance).
Of course, I could gesture at my wife while saying "our son," but is there a verbal way of indicating the child belongs to myself and my wife without saying something long and awkward like "the son of my wife and myself" or "I and my wife's son" or "me and my wife's son" etc.?
The comments make sense; I guess I should have presented the scenario as my wife not being there; if in the course of the conversation I mentioned my wife, and then later my son, but said that ("my son" -- or "our son") those expressions would seem even awkwarder to me (without my wife present). But the commenter is probably right that I'm overthinking it.