This study investigates diversity within the population living on their own in mid-life in the United Kingdom by analysing partnership trajectories into solo-living in mid-life, and the kin availability and socio-economic characteristics of middle-aged men and women living alone. Despite the rise in living alone in mid-life since the 1980s, in particular among middle-aged men, there has been little scholarly attention for the diverse pathways into solo-living, how these differ by gender, and how these influence the socio-economic composition as well as the care and financial resources of those living alone in mid-life. In this paper, we first argue that the partnership and parenthood trajectories of those living on their own in mid-life are diverse and discuss how these might differ by gender and between socio-economic groups. We then use data from the General Household Survey (GHS) to describe the trend in living alone for the period 1984 to 2009. Next, we use the first wave of Understanding Society (USoc) (2009-10) to analyse the partnership histories, kin availability and socio-economic characteristics of those living alone in mid-life. The findings indicate that the dissolution of a marriage with children is the dominant pathway into mid-life solo-living, but also that there is a substantial group of never-partnered men living alone with both low and high socio-economic status. We discuss how we can make a distinction between different “types” of people living alone in mid-life and stress the policy implications of the heterogeneous composition of the population living alone in mid-life.