But that's the thing. You don't know enough about it to call it an emotional affair, even if if your SO doing it. Unless your SO has told you that they have intimate, romantic feelings for the other person.
And really, there is no sole definition for any one thing. Language is not prescriptive. I disagree with the definition that you gave, and have told you why. You ignored that in favour of an argument from authority, which is fallacious.
Finally, you write an awful lot for someone who doesn't give a shit.
I repeat; why would it?
What if they don't realize they have intimate, romantic feelings? There are plenty of people who have no idea that they love someone until someone else points it out. Sitcoms are built on that shit.
So if your boyfriend thought that your relationship with another male friend was inappropriate, then it would be?
I don't think you believe that.
Yes, it would be. If he feels it is inappropriate, then it would be because it is hurting his feelings. I think that if I disagreed and maintained the relationship behind his back, then I would be engaging in an emotional affair regardless of whether I think it is platonic or not because my emotions (romantic or otherwise) would be invested in a way that was unhealthy to our relationship.
Am I the only one who finds kissing on the lips between family members a bit odd?
Lip-kissing on family is fucking weird. Even with my girls, I go a half inch above the head and make a smacking noise. Unless I'm sleeping with you, you don't get kisses on the face if you're over a year old. That's all there is to it.