Hello! I have 2 6-month old boys and 2 2yr-old girls. I introduced one boy and one girl and they did nothing. I introduced the other boy and the other girl and they both went nuts (in a good way)! I don't understand why the first two didn't even attempt to get to know each other. Any thoughts? Also I really wanted to have a litter of guinea pigs which is why I got girls in the 1st place, but I just learned that pregnancy isn't good on guinea pigs. So should I just not allow it to happen? Thanks!