The children - Edith Wharton

On a cruise ship between Algiers and Venice, Martin Boyne, an unmarried engineer in his forties, encounters a wild, ebullient menagerie of stepbrothers and sisters, kept together as a 'family' by the efforts of the eldest, the lovely, fifteen-year-old Judith.
Caught between genuine outrage at the plight of the precocious and fought-over children and his disturbing feelings for their fifteen-year-old sister-protector, Boyne finds himself increasingly drawn to their enchanting, improper and liberating ways.
But awaiting Boyne in Switzerland is Rose Sellars: tactful, genteel, old New York incarnate, patiently anticipating marriage.
Caught between old money and new, Martin Boyne is a tragic and poignant knight errant caught on the cusp of a changing world.