Double first cousin

Template:Linkless-date Double first cousins arise when two siblings reproduce with another set of siblings and the resulting children are related to each other through both parents' families. Double first cousins share both sets of grandparents in common and have a higher degree of consanguinity than ordinary first cousins.

When identical twins reproduce with a set of siblings the resulting children are triple first cousins. When identical twins reproduce with identical twins the resulting children are quadruple first cousins (genetically indestinguishable from full siblings).