Is it considered disbelief for a Muslim to permit his brother to play games that contradict the creed?

It appears the questioner is afflicted with waswasa (whispers/obsessive thoughts) concerning disbelief (kufr). He is advised to desist from indulging in these waswasa and to turn away from them, seeking refuge in Allah for well-being from them. Merely allowing oneself to play games that contain doctrinal transgressions does not constitute kufr.