The Tower and the Hive — Anne McCaffrey

For generations, the descendants of the powerful telepath known as The Rowan have used their talents to benefit humanity. As human civilization reached out to colonize the stars, the family led Earth to ally itself with the peaceful alien Mrdini. Together, the two races have held back the predatory Rivers, who once decimated entire worlds. But there are factions on Earth who resent the power the family has accumulated. Now, with their goals of peace and prosperity so close at hand, The Rowan's descendants face the looming destruction of all they have suffered to achieve...