Fate Had Other Plans (The Maren Lofton #5)
Phil Oleson

Jon Fitch, while trying to comfort his fiancé, wishes he could spend more time with his thirteen year old son Ken, who lives with his Mom, Candace McGraw, on the Caribbean Island of San Roussel. Ken seems happy in this Island paradise and he sails regularly with his Mom and her boyfriend James Robinson. Knowing that a marriage between them could be in the offing, Jon's concern is that the relationship with his son may drift away. That may not be the only problem this teen faces.
This is the fifth book in the Maren Lofton series.