Am I ruining my guinea pigs friendship

I've had a guinea pig for about 4 months, when I decided to get another one. The one I got was 2 months old, and the other one I had was 7 months old. Besides the occasional teeth chattering, they got along GREAT! Then, one night when my friend came over, they starting nipping eachother during floortime! I know this is not serious, but they've never nipped eachother before. Everyday now, it seems like they start getting more and more aggresive towards eachother, but so far, none of them have drew blood. I'm just wondering if I'm the one who has to do with their friendship breaking up? I feel so sad that this is happening. Someone please give me a decent answer...

(And yes, I have read cavyspirit.com/sociallife)

Ok, did you get two males, two females? A male and a female? I can't give you a straight foward answer, but i can push you in the right direction,

If you have two males or two females, then what is happening is that as the guinea pig gets older they tend to be more territoreal. Unless these guinea pigs were raised together from day one, they usually start to get aggressive towards one another,*even if they where raised together there still is that chance they will get aggressive* . You are probably gonna have to seperate them as they get older if this behavior doesn't stop. Try telling the guinea pigs NO as they nipp at each other, by lightly tapping on *BOTH* their noses and saying no.

If you have a male and female, then chances are that the male wants to make baby with his sexy female! lol. And even then u still have to seperate them.