Do you mean... if I raise two BGK together...
I've tried keeping multiple baby BGK together on several occasions. Everytime I've tyried they have fought to the death as soon as they meet. I've never tried it with older BGK as at larger sizes I wasn't willign to risk injury or death.
There have been a few others that report success at keeping multiple BGK together, but it seems the odds will be against you...
I've questioned people at great length who found success at housing multiple BGK, I've never been able to find a consistent detail that appeared to be the 'trick' in making it work.