This thesis addresses the issue of the moving boundaries between family and friends' roles inpersonal networks, adopting a life-course perspective and using Switzerland as a case study. In aperiod of major changes in personal life happening in contemporary Western societies,understanding the organization of personal networks intertwined with the unfolding of individuallife courses is of prime importance in facing new challenges with regard to social integration.The data stem from a representative national survey carried out in 2011 named Family tiMes, including 803 individuals born either in 1950-1955 or in 1970-1975. An innovative research designwas adopted, combing cross-sectional ego-centered network data and retrospective longitudinal life-course data.The results show continuing boundaries between family and friends' roles and that family keeps aprominent role in personal networks despite the notable importance of friendship ties. Onerelationship stands out above all, that with the partner, followed quite a few steps behind by thosewith children. Regarding life courses, de-standardization tendencies were found in family formationand also a persistent gendering of occupational trajectories. Two kinds of life trajectories areparticularly intertwined with personal networks, co-residence and partnership trajectories, bothrelated to the unfolding of family life. In particular, transition to parenthood functions as a turningpoint in individuals' lives, deeply transforming their sociability. Finally, a twofold pluralizationprocess was identified, affecting simultaneously the organization of personal networks and theunfolding of individual life courses. This thesis contributes to the literature on the sociology offamily and personal life, and to fruitful interlinkage between the network approach and the life-course perspective.