Moon Tide — Rachel E. Rice

When the young Alpha werewolf Hunter, returns to his home from his harrowing escape in Alaska, he discovers that the human he loves has taken up with his twin brother. He sees this as a betrayal by his brother Devin and Katie.
Unhappy at being alone, Hunter decides it's better to share Katie with his werewolf brother than to desire her and never have her. If Hunter makes that faithful decision he will have put aside his principles and all that he believe in for one night with Katie.

Haley is the teenage human who loves and desires Hunter above all else. But Hunter can't seem to see her because he wants Katie. If Haley doesn't find a way to Hunter's heart, and Hunter wakes up too late to discover that Haley is the only one for him, he could lose Haley to a lion shifter who is on her trail, and he won't stop until he brings Haley into his Pride of six females.
This is book six of a seven or eight book series. Book 1 is free.