This was posted on Jokers:

CrystalEiserman Crystal Eisermann
Got a little inside scoop about BB13 today.... And I gotta say, I'm not excited. Matter of fact, I'm a little scared....

CrystalEiserman Crystal Eisermann
Riddle me This, Riddle me That.... Rumor has it, three Duo's will be coming back.... One you love, One you hate, and One you love to hate.

And the girl posted on another BB forum with more:

I can only be vague for now, I apologize!! But I got some news today (from an EXTREMELY reliable source).... and it not only didn't excite me... it scared me.... so, thats all I can say for now. I LOVED one pair, and I liked the other one while they were on the show, since the show it's been bitter sweet with one duo, as in one member is sweet, the other is bitter! And the other duo, everyone loves to hate, including me, haha.

And yes, all 3 are returning. I originally heard that only one person from each pair was going to go in, like One person in the duo would compete against the other for a spot in the game, but that is less likely from what I was told today. And I know I am annoying being vague, but honestly, I'm probably in trouble for even saying what I did, but I was reading all the speculation and had to jump in, lol