Steve/Tony
Steve was laughing again, holding his sides. "Tony, I don't think we'll ever be done with dares. In fact, I think I'd be sad if we stopped. Pushing your buttons is way too entertaining." The conversation may not have delved too far into embarrassing territory, but Steve would still be humiliated for admitting such a thing later. He liked to pick on Tony because he liked him -- probably something that Tony was already well aware of. But Steve really had no business freely saying these things out loud.
"That's still so bizarre to me; the two of them. How does that even work? And now they're engaged?" Steve paused, realizing whatever underlying doubts he had about the couple was beginning to show. "I guess I should be saying I'm happy for them, shouldn't I?"