Who is Grant Kavanaugh from The Neutronium Alchemist Consolidation and what is their importance?

Louise and Genevieve's father is the master of the vast Cricklade estate. After taking the local militia to the nearby city of Boston to quell what is believed to be communist uprisings, Grant is possessed by Quinn Dexter's former possessor, who Dexter manages to force out of his body and into Grants.