 Limiting offspring numbers in order to reduce the likelihood of accidental consanguineous relationships between offspring of the same donor was initially proposed by individuals concerned about possible risks of congenital disease (Curie-Cohen 1980). Recent work has attempted to quantify these risks (De Boer et al. 1995; Wang et al. 2007). While the increased risk of congenital disease resulting from unintentional consanguinity is dependent on the size of the population served by a sperm bank, the risk is lower than might be initially thought. For instance, Dutch models suggest that an offspring limit of up to 25 would not result in any significant increased risk, given their particular demographic makeup (De Boer et al. 1995). However, there is also the risk of psychological harm for individuals that discover they have unwittingly entered into a consanguineous relationship, given the associated social taboos (Wright 2016). Furthermore, there may be legal complications if an accidental consanguineous marriage is discovered after the fact (Cahn 2009a). One way to mitigate these risks without imposing offspring limits would be to increase openness in gamete provision, including actively informing individuals about the identity of their genetic siblings. However, even in the absence of such measures there is little agreement about how the risks associated with consanguinity should be translated into offspring limits, especially given the broad reproductive freedom individuals are generally afforded (Wright 2016; HFEA 2011).