Friendship and Obligation: Sibling Relationships and Illegitimacy in the Early Modern Spanish Nobility

The early modern Spanish nobility often had large and complex families which could include children of different marriages, illegitimate siblings, and a huge potential for family conflict. This paper draws on wills, lawsuits, and legitimation petitions from the early modern Spanish nobility to focus on the relationships between legitimate and illegitimate siblings. I argue that many legitimate siblings were aware of their illegitimate half brothers and sisters and worked to protect and defend them as long as their existence did not disrupt the smooth transfer of property between generations. Family records reveal that illegitimate children often had financial and social relationships with their legitimate siblings and their aunts and uncles, creating several generations of sibling relationships that they could draw on for support. On the other hand, the presence of illegitimate male half-siblings could threaten the inheritance of legitimate daughters or the brothers of the title holder, creating lawsuits, disputed titles, and family feuds. In spite of the potential conflicts, however, these records suggest that the nobility genuinely valued children (whether legitimate or not) as beloved family members and as potential heirs, marriage partners, and future allies