Justin Bieber & Sofia Richie: Besos de Cumpleaños en Cabo

Justin Bieber and Sofia Richie are celebrating her 18th birthday with a lot of swapping spit, cuddling and even a little nudity.

The two are down in Cabo ... and it's clear to see, there's an awful lot of chemistry between the new couple. Richie turned 18 Thursday and the two got on a private jet Friday to head south of the border.

Justin doesn't seem too shy to show some skin either, dropping trou right next to a butler.