Twins that have sex with each other
For other uses, see Twincest disambiguation. Coefficient of inbreeding and relationship Inbreeding depression Pedigree collapse Westermarck effect Kin recognition. Related Otger. Take a look at the biology that determines the sex combinations that are possible with identical and fraternal twins. These are known as Braxton Hicks contractions and can be uncomfortable, but they're perfectly normal and there's no need for alarm. Skip to content. Does being a twin increase the likelihood of having twins?