Sextuplets are a set of 6 offspring, all born from the same birth. Parents expecting sextuplets will encounter special joys and challenges as they prepare for this rare type of pregnancy and birth. Sextuplets can be fraternal (multizygotic), identical (monozygotic), or a combination of both. Multizygotic sextuplets occur from six unique egg/sperm combinations. Monozygotic multiples are the result of a fertilized egg that splits into two or more embryos.

Source: Very Well Family