Chin Fight

Hello,

I have 2 male chinchillas who are both 6 year old. I have owned them both since they were kits and they are actually brothers. They have spent their entire lives together in a double FN and always got a long great cuddling etc. This morning I woke up to barking and when I went over to them I could tell they had gotten into a fight- Some small cuts on each of them and fur slips. They were still chasing one another and I immediately separated the two of them, but I am just so confused why after 6 years this would occur.

Any advice or ideas about why this might have happened?

I am also guessing it would not be safe for me to put them back together?

Thanks so much!