How do families mobilize to respond to their members’ needs? How do families transmit advantages and disadvantages within and across generations? Most of what we know about these questions is restricted to solidarity and transmission in the nuclear family – a small segment comprising only the closest kin. The project’s core concept – the kinship matrix – offers a much richer view of family members and family ties relevant to solidarity and transmission. It widens the lens to examine nuclear family ties in a larger pattern of relations that constitutes the immediate and extended family network spreading vertically and horizontally. Based on this concept, the project will achieve three objectives: to collect new comparative data on the kinship matrix in five European countries (Objective 1); and to use these data to conduct novel studies of solidarity (Objective 2) and of transmission (Objective 3) that break new ground in family research. The project comprises three subprojects, each dedicated to one objective. Subproject 1 will achieve Objective 1, collecting and preparing data on kinship ties that underpin all analyses on solidarity and transmission. The new comparative survey on the kinship matrix will be supplemented by further sources of population-scale data. Subproject 2 will achieve Objective 2, capturing solidarity in a multigenerational structure of immediate and extended kin. Subproject 3 will achieve Objective 3, capturing status transmission and behavioral transmission across a wide set of relevant kin. All subprojects will study the channels of solidarity and transmission, combining attribute data on status and behavior with relational data on the quality of kinship ties. The project will advance our understanding of the family as a unit of cohesion constitutive to the European social model and as a unit of transmission constitutive to inequality within and across generations. The new data will be released to create a lasting impact on family research.