In Cognitive Radio (CR) Networks, the licensed but vacant spectrum bands are shared by the unlicensed users (CR users) in an opportunistic manner. The CR users should operate and cohabit in the licensed bands without causing any interference to the Primary Users (PUs). This CR user cohabitation which is managed by a spectrum coordinator, enables several design challenges. Therefore, A User Cohabitation Coordinator, UCC, should be designed considering the heterogeneous Quality of Service (QoS) requirements for the CR users and the short-term fluctuations in the available licensed spectrum bands. Moreover, the spectrum coordination among the CR network operators for CR users should also be considered by the UCC for an effective and fair spectrum sharing. Considering these challenges, the main contribution of this paper is to design a QoS-based spectrum coordinator for CR user cohabitation in order to achieve high throughput and fairness. The proposed UCC uses the first-difference filter clustering and correlation based PU modeling to integrate the fluctuations of the PU activities into the spectrum sharing. The UCC characterizes the QoS requirements of CR users by adopting queuing theoretic models. The proposed scheme enables the cohabitation of the CR operators dynamically. The evaluations demonstrate that the proposed UCC provides high throughput while maintaining the fairness in the CR networks.