This volume continues the work of the International Academy of Estate and Trust Law in 2003 and 2004 in examining through the juxtaposition of civil and common law jurisdictions areas of fundamental importance to estate and trust lawyers internationally. Here we focus upon two themes: the definition of "family" and the impact of the expansion of the concept of "family" in law; and family fights over wills and estates that recourse family members may have in challenging an estate. The first Part, The Challenge of the "New Family" for Law, considers the "challenge" both in the inter vivos and the postmortem contexts in the United States, Canada, France, the United Kingdom, Australia and New Zealand. A particular focus is upon the dramatic expansion of the definition of family from the "traditional" nuclear family consisting of a husband, wife and their mutual children to a definition that includes unmarried heterosexual and same sex couples living together and, in some jurisdictions to new kinds of companionate partnerships that are not based on a sexual relationship. The second Part, Contesting Wills and Intestacies, examines the law in Australia, Switzerland, France, Mexico, and the United Kingdom. In its comparison of civil and common law approaches we see how the law expresses the same principle objects "protection of family and obligations towards key family members" but does so from entirely different perspectives; and where the common law which enshrined the notion of testamentary freedom is being qualified through the expanding domain of family provision legislation, the civil law which is based on codified shares and allocated responsibilities expressed through proportionate entitlements in estates, is being qualified through a range of disqualifying and varying mechanisms. This volume is the fifth of the published deliberations of the International Academy of Estate and Trust Law. It contains the work of solicitors, barristers, notaries, judges and Professors of Law in areas of Trusts, Inheritance and Succession law, Tax and Comparative law. It will be of interest to practitioners and scholars alike in the area of trust and estate law.