8:00 AM PT -- Sources connected with the exes -- who were there last night -- tell us "the kiss" was peer pressure fueled. We're told Marc and Jennifer only did it because the crowd was chanting "beso," and it would've been awkward if they didn't.
Marc won Person of the Year at the Vegas shindig. Before he was honored J Lo came out and the 2 performed their duet, "Olvidame y Pega la Vuelta."
Let's not forget he's remarried -- but during his speech, in what seems to have been damage control, Marc expressed his love for J Lo ... as a sister! (For non-Spanish speakers it starts at 17 seconds).
Take a look Jennifer's expression.
Marc's now posting multiple shots of him planting one on his bros last night. Seems like he's trying to make a point about casually kissing lots of people.
Tell it to the missus, Marc.