The Bonded

One family lives as genetic launchpad for the Bonded, a human evolutionary side-branch. ‘The Bonded’ have a communal mind, and they've coexisted with humans since prehistory. The book begins as a young forensic scientist and his mentor investigate a series of violent crimes. They learn an unknown group is involved, and one 'woman of interest' turns out to be a prominent member of the Bonded. She has the ability to cheat death, and has lived for centuries. She also turns out to be their mother. Each individual Bonded member sees the hive mind in addition to their individual consciousness. The group must juggle that combination. Ultimately, a competition breaks out for evolutionary advantage. The conflict results in catastrophic nuclear war, leaving all who survive to pick up the pieces.