Henry Vere De Stacpoole 
The Blue Lagoon & The Garden of God (Sequel) [EPUB ebook] 

The Blue Lagoon tells about two English kids marooned on a tropic island during a huge storm. Their only adult company is an aging sailor, who fathers the kids until their teenage years and dies. They both grow up, finding food in the wild and falling in love with each other, until one day, a fate drives their little family unprotected into the open ocean. Yet, the father of the boy makes a rescue expedition and it turns out the two boats sail to meat each other. The second book of the sequence tells about the life of their son, Dick, who repeats the fate of his parents and lives on a deserted island where he finds love, occupation and exciting adventures.