Flight into Passion — Em Ashcroft

Only after Weston Great Wing slept with Robyn does he realize she is the wife of his greatest enemy. But it's too late-Robyn is his breedmate, and she is bonded for life to Weston and his breed partner Thane. What's more, Thane is missing, kidnapped by the Grid. Robyn has avoided eagle shape-shifters ever since she slept with Thane on the night she decided to change her life. For years she has fought to destroy the organization that her ex-husband financed. Now she has to work with Weston to get Thane back. Thane understands Robyn's struggle better than Weston, but his stubborn breed partner won't accept the inevitable. He has been in love with Robyn for years, but his breed partner is as essential to him as she is. If they can't live together, Thane must choose. Unless they can persuade Weston to accept the loving menage Thane and Robyn desperately want. Note: This book contains double vaginal penetration.