Faith by Helen Scott Taylor

Two-and-a-half years later, Faith’s bottle washes up on the Scottish coast.
Single dad, Hew Mackenzie, lives in the shadow of his successful siblings, always the odd one out. A terrible experience with a woman shaped his life, and he turned his back on romance and dedicated himself to working on the family estate in the Scottish Highlands. He’s certain he and his son, Fergus, are best off alone. Fergus has other ideas. When he finds Faith’s message in a bottle on a Scottish beach he gives it to his dad for Christmas. Might Hew be the dream hero Faith is searching for?