There is no official or universal definition for the concept of ‘family’. The absence of EU legislative competence in the substantive family law field means that there is no ‘EU family law’. Thus it is the individual EU legal instruments in different policy areas and the jurisprudence of the Court of Justice of the EU that demarcate, on an ad-hoc basis, the contours of the concept of ‘family’ and of related concepts for the purposes of EU law. The chapter argues that in recent years, increasing focus has been directed towards the way EU law addresses diverse family constellations in its laws and policies and how it manages the interaction of different national family law regimes in situations which fall within the scope of application of EU law. It is explained that the EU legislature and, especially, the Court have been faced with a plethora of complicated questions involving family-related matters and – as a result – with the unenviable task of carving out a solution that can be tolerated by all Member States. After identifying some pertinent questions, the chapter proceeds to explain how the chapters in this volume engage with these issues.