Palindrome by Stuart Woods

Palindrome - Liz Barwick has been beaten nearly to death by her husband.  Her friend, Ray Fergusen has offered his cottage on Cumberland Island to recuperate after she leaves the hospital and to capture the beauty of the island in photographs.

Cumberland Island is run by Angus Drummond who is now over 90.  His grandchildren, Hammish and Keir (twins), Germaine (who runs the inn) and James Weathers stand to inherit.  Weathers wants to develop the island, nobody else does.
Hamish and Keir have refused to have anything to do with each other and will not even acknowledge they have a brother since they were 18.