It’s good that they are both neutered, but as kurotta is implying, putting two neutered brothers together does not create a strong bond. After a neuter, hormones fluctuate for about a month, and following that, rabbits need to go through a formal bonding process in order to truly be bonded and be together, unsupervised, for long periods of time.
It sounds like they are not ready to be together permanently. There is a bonding info page on this website that outlines steps to take in order to bond rabbits: https://binkybunny.com/BUNNYINFO/tabid/53/CategoryID/9/PID/940/Default.aspx
.. as babies, there are no hormones so rabbits get along just fine. Unfortunately, once the hormones develop, even after a neuter, bonding is needed to ensure a healthy, happy relationship.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.