Tess and the Highlander — May McGoldrick

Tess
Tess Lindsay has spent most of her life on the remote Isle of May, uncertain of her identity. Raised by the two sole inhabitants of the island, she is left to fend for herself after their deaths, until a stranger washes ashore in a storm. Tess pulls him from the surf, not knowing that in saving the Highlander she is saving herself.

The Highlander
If good looks and a taste for adventure are a curse, Colin Macpherson is destined for ruin. Until he ends up a castaway on Tess's windswept island, he's been roaming the seas, seeking fame, fortune...and a different girl in every port. But his fascination for this strong-willed lass goes beyond her wild beauty, intriguing him as no girl ever has.

As Colin gains her trust, Tess reveals what little she knows about herself and her past. From her scant clues, though, Colin comes to one conclusion: He must return Tess to the mainland to reclaim her birthright, even if it means losing her to a destiny that does not include him.