This thesis supports the recourse to habitual residence in international family law as an inter-country concept, which is old in its origins and modern in its objectives. Habitual residence is adaptable and flexible when considering each family context. It is actual and close when determining the realistic nexus with justice. According to this research, the possible transnational conflicting operation of habitual residence, affecting people's interests and rights in similar family contexts, does not rely on the absence or presence of an international legal definition, but on the lack of uniform factual guidance. A uniform fact-based determination, life adapted, is therefore required for the most effective and efficient use of habitual residence. In this sense, an international handbook should be conceived at the Hague Conference on Private International Law, with the support of other entities, in order to establish a guide applicable to the various family law instruments adopting habitual residence.