The impact of the intrinsic decoherence on the dynamics of a system composed of two coupled qubits inside a two-mode cavity with a nondegenerate parametric amplifier is analytically investigated. High-order nonlinearity causes strong entanglement and mixedness, which are analyzed by using entropy, negativity, and log negativity. In the absence of intrinsic decoherence, it is found that qubit-qubit coupling improves the generation of population inversion, entanglement, and mixedness. The coupling acts as external decoherence in the presence of the intrinsic decoherence, and the quantum effects evolve monotonically to non-zero stationary values. The qubitqubit
entanglement is crucially dependent on the nonlinearity and the intrinsic decoherence. The stability of this entanglement is granted for small intrinsic decoherence.