Spontaneous group communication can be attained by deploying Mobile Ad Hoc Networks (or MANETs). The limitations thrown by these networks, motivate the necessity of a group key management framework to secure data traffic. In this context, significant research work done in the last decade and proved that the trust based frameworks deliver better performance than others. Trust value can be evaluated based on direct and indirect interactions with other nodes in the network. The threshold trust value does binary classification about a node is genuine or fake (misbehavior) and further communication includes or excludes. However, in many automated systems, the result for a given input cannot be just categorized as binary output. Instead of a binary, it is more spontaneous and natural to use a fuzzy set based classification which gives the degree of genuineness. To realize this concept, we propose a reliable group key management framework by adding fuzzy logic rules in this paper. The clustering scheme with Fuzzy classifier aids, to eliminate the pretended nodes over a span of time in order to evade internal attacks. Moreover, it saves the energy of each node due to lightweight framework and less key management overhead. Our simulation outcomes prove that our method is more reliable compared to existing frameworks.