Secure multicast communication is important for applications such as pay-per-view distribution. LKH has been proposed to distribute a shared secret key in a way that scales efficiently for groups with many members. However, the efficiency of LKH depends critically on whether the key tree remains balanced. For applications such as video streaming or online teaching, several multicast sessions might be related in one way or another. in this paper, we consider the balance of the key tree and treat related multicast sessions as a whole. Our approach shows significant improvement over traditional method and trades off additional rekeying costs for similar computation power at members'. side compared to existing related approach. Two optimisations are also proposed to further enhance the efficiency of our algorithm.