Book excerpt: In many Western societies, there has been a tremendous increase in family diversity over the course of the past few decades, resulting in a considerable prevalence of non-traditional family forms. The increased instability of marital and non-marital unions entails new challenges for both parents and children. In this special issue, family studies scholars from different disciplines examine from a life course perspective how re-partnering processes work and how family relationships are rearranged in order to adapt to the altered needs and requirements of post-separation family life.