Growing up together, siblings or not, means nothing in the world of lifelong rabbit bonds. Rabbits will fight and mate among family so any notion of childhood bons are lost.
A stable, proper bond will not include ANY mixed signals, as you’re seeing, so no, they are not bonded, or at least it is an unstable/weak bond that needs work before considering leaving them together unsupervised.
How old are they and are they neutered?
Based solely on your description and making assumptions, I assume you got these two males as young rabbits (i.e., less than a year old, not neutered), so what you observed is called a baby bond — A baby bond is a bond held together simply because one or both of the rabbits have not yet reached puberty, therefore there are no hormones urging them to mate/fight/defend. It is generally considered a temporary bond that you cannot predict when it will dissolve because we can’t tell when hormones will “take effect” essentially. If that is the case here, you need to house both rabbits separately for their safety — they have no bond and two intact males are the most dangerous combination to keep together. They need to both be neutered, you then need to wait 1mo post-neuters (for hormones to settle), then you can begin the bonding process, outlined here: https://binkybunny.com/infocategory/bonding/
If both these rabbits are well past 1mo neutered, then what you have sounds like either a weak bond or a broken bond. Either way, it means monitoring if problems occur in the near future and if so, using the bonding tactics in the Bonding link in the last paragraph to do some rebonding and solidification of the bond in a safe way.
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.