I have 2 brothers, 1 came to me at 8 weeks old and another went to a colleague of mine. To cut a long story short, I ended up with both and they are bonded in a group of 7. I don't think they know each other, they pretty much stay away from each other, and when they do go near they often end up having a little tiff. So if they do remember each other they don't like each other very much, they were only apart for 3 months.