First Love by Fiona Davenport

Tucker Carrington knew what true, lasting love looked like. He grew up surrounded by it, but he never expected to feel it for himself when he was only twenty-one. Let alone for Eva Kendall, a girl he’d known since she was born. His best friend’s sister.
Since Eva was too young for him, Tucker had to wait for the right moment to make her his. Heading overseas for his father’s company, the distance didn’t stop him from keeping an eye on Eva. Because she was his first—and forever—love.