A coupled framework of reduced order models (ROMs) for addressing the nonlinear aeroelasticity problem is introduced. A procedure to develop CFD-based reduced order models (ROMs) which capture the essence of an aerodynamic system while reducing the complexity of the computational model is introduced. An Eigensystem Realization Algorithm is used to convert ROM unsteady aerodynamics into the LTI state space model. A reduction in the cost of the realization of the ROM kernel is obtained by the identification of the state-space model. Structural nonlinearities (hardening nonlinearity on the second mode) are included in a nonlinear time invariant structural ROM. Structural ROMs are identified for cases where the thermal load is added and the thermal effect on the aeroelastic response is studied. Aeroelastic analysis is conducted using the nonlinear state space model. The weakened wall-mounted AGARD wing 445.6 has been used for validation. An aeroelastic analysis of a NACA 65A004 composite wing model is also conducted at supersonic speeds including structural nonlinearities due to thermal load. The state-space model is a highly optimized decoupled system while retaining significant details of the aeroelastic system. The proposed approach is computationally efficient while including structural/aerodynamic nonlinearities.