Complex sentence: His birth place is Kerplop-it-goes Island (named after the Galápagos Islands); on his 21st birthday, as dictated by nature, he is required to go back to the island for a period of time.
Split into simpler sentences: His birth place is Kerplopitgoes Island (named after the Galápagos Islands). On his 21st birthday, as dictated by nature, he is required to go back to the island for a period of time.