The Playboy Twins -- When Sisters Suck Face ...

8/10/2010 8:30 AM PDT
Playboy Playmates and biological twin sisters Karissa and Kristina Shannon, 20, got a lot closer at the Playboy mansion this weekend ... and shared a tender open-mouth kiss with each other.

It's OK to love your sister ... but is it really OK to LOOOOOOOOVE your sister?