Two cats licking each other's fur may indicate a good relationship between them. Moreover, frequent licking allows each cat to develop its own scent, thus fostering closer bonds.
Of course, grooming is a way for cats to assert dominance. Generally, after two cats have established their hierarchy and spent time together, the higher-ranking cat will groom the lower-ranking cat. This serves two purposes: firstly, it's a way of asserting dominance, and secondly, it's a symbol of friendship, indicating that they have accepted each other. If you, as a pet owner, find that they don't allow each other to groom, it's very likely due to mutual resentment. In this case, it's essential to separate them to prevent a fight.
