Guinea pigs...horny??

I have a 2 month old guinea pig, Oliver. I just got a 2nd named Chester who is 1 month old. Well, we were holding them and Chester was trying to nurse on Oliver and Oliver was Chester anyays in the cage it was the same. Chester is half the size of Oliver. Oliver... got me wet, you know. Chester doesnt seem interested. They are both boys. Anyways, is this normal, how long does it last? Please help!