The association between individuals’ criminal behaviour and the criminal behaviour of their in-law family members is central to the current study. The criminality of extended family members may pose a risk of (persistence in) criminal behaviour. Data are used from the fourth generation of the Dutch Transfive Study, which contains demographical data as well as and conviction data on family members from consecutive generations of families. Results show a significant association between convictions of individuals and their in-law family members, over and above the effect of having a convicted partner. The strength of the association depends on the severity of the offense as well as on gender. Similarity in convictions before marriage as well as indications of continued similarity after marriage has been found.