The pygmy marmoset is a non-seasonal breeder and usually gives birth to twins once or twice a year.[23] However, single births occur 16% of the time and triplet births 8% of the time.[2] The pygmy marmoset is usually monogamous though there is some variation within the species in terms of breeding systems. Polyandry also occurs as male marmosets are responsible for carrying the infants on their backs. Having a second male to carry the offspring can be beneficial as marmoset litters are often twins and decreases the cost to any particular male.