Based on

Movies like La figliastra - Storia di corna e di passioni (1976)

A long time ago in Sicilia, there was a common, unwritten law that linked the hereditary rights to unequivocal demonstrations of virility. Because of that traditional law, a middle-age widower whose wife died without begetting him a child, is about to lose an inheritance of a large sum of money. The man marries again, with Nadia, an attractive woman with a daughter from her first marriage, Daniela. But time passes, and Nadia is not getting pregnant, either. Eventually, his beautiful stepdaughter will help him solve his problem.