In my understanding they all start off as juveniles with the most dominant one progressing to a female and the next most dominant progressing to a male. So, I think that unless they have already turned into a male and female, you're basically looking at them needing to establish dominance so they'll battle at least a little bit. I've paired up a male and female that each lost a mate and they took a few hours to get together, but I've also seen where they run into issues with each other when they are too similar in size.