I have a father/son duo that get along famously. I think it's all based on the personality of the piggie themselves as to whether or not they will get on in a pair though. I think part of the reason that my two guys are compatible is that I introduced the baby gradually to his father over a period of the first few weeks of his life and then moved him in permanently at three weeks old. I've been keeping a close eye on them, as I'm concerned about dominance issues arising as my Nigel (the baby) is approaching 6 months in age, but so far so good. His mother and sisters and other female cage mate squabble more so than the boys to be honest!