We assessed, using the Swedish national census and total population registries, the cohabitation status of the sibling pairs as the proportion of possible years lived in the same household until the oldest turned 18, the age of majority in Sweden. We defined pairs as “reared together” when this proportion was ≥ 80%, which was the full- and half siblings used in this report. We included all possible pairs, meaning some individuals were part of more than one sibling pair, for a total of 393,972 unique pairs made up of 670,836 unique individuals.
