What are the three main types of kinship recognized in social structures?

The three main types of kinship recognized in social structures are indeed bloodline, marriage, and adoption. Bloodline refers to the biological relationships among individuals, such as those between parents and their children or among siblings. Marriage introduces legal and social connections, establishing a family unit that may not be biological but is recognized legally and culturally. Adoption further expands the concept of kinship by legally formalizing relationships between individuals who may not share biological ties but are recognized as family.

This answer reflects the standard frameworks of kinship in many societies, acknowledging the importance of both genetic and socially constructed relationships in the formation of familial ties.