Each Concentrate revision guide is packed with essential information, key cases, revision tips, exam Q&As, and more. Concentrates show you what to expect in an exam, what examiners are looking for, and how to achieve extra marks. This chapter focuses on family relationships, marriage, same sex marriage, civil partnership, forced marriage, and cohabitation, beginning with a discussion of the absence of a widely acceptable definition regarding the concept of ‘family’. It examines how marriage was defined in Hyde v Hyde (1866), and the definition of civil partnership under the Civil Partnership Act 2004. The concept of ‘common law marriage’ and the rights of those cohabiting is considered, along with the importance of formalities to end marriage and civil partnership. It also highlights the rights of parties to a marriage or civil partnership to acquire rights over property during the relationship on the basis of trusts law or proprietary estoppel. Finally, it looks at calls to reform the law in relation to cohabitants, particularly with regard to joint ownership of property.