All books in this flagship series contain carefully selected substantial extracts from key cases, legislation, and academic debate, providing able students with a stand-alone resource. This chapter first considers demographic data on family relationships in England and Wales, and then examines the treatment of ‘trans’ people in this area of family law; and the history of legal recognition of intimate relationships between parties of the same gender, culminating in the introduction of same-sex marriage and mixed-sex civil partnership. This is then followed by discussions of status-based relationships (marriage and civil partnership); creating a valid marriage or civil partnership; grounds on which a marriage or civil partnership is void; grounds on which a marriage or civil partnership is voidable; and non-formalized relationships (cohabitants and other ‘family’).