Cohabitation is when a couple live together in one household but are not legally married. Cohabiting couples do not have the same legal protection as married couples. In 2016 there were a total of 18.9 million families in the UK with 3.3 million comprising of cohabiting couples. Cohabiting has more than doubled since 1996 from 1.5 million to 3.3 million in 2016.