Types of twins
Identical (monozygotic) twins were the result of a single fertilised embryo splitting in two, creating two people who shared an identical genetic makeup, and typically looked exactly the same physically. Fred and George Weasley were monozygotic twins whose appearance was so perfectly identical that they were capable of tricking their own mother into mixing them up as a prank.
Fraternal (dizygotic) twins were the product of two independent fertilised embryos. Unlike monozygotic twins, these twins were not genetically identical, being no more related than any non-twin full siblings. This meant that one fraternal twin could be born magical while the other was not, as was the case with Martha Steward (Squib) and Rionach Steward (witch), the daughters of Ilvermorny founders Isolt Sayre and James Steward. Male-female twins were, by definition, fraternal twins, with the rare exception of identical twins where one twin's anatomy did not develop normally due to a disorder or where one twin turned out to be transgender.
Conjoined twins were monozygotic twins resulting from an embryo that failed to completely split. This resulted in two people who were not only genetically identical, but physically connected, often sharing internal organs. The "2-Headed Baby" that toured with the Circus Arcanus in the 1920s was a set of conjoined twins.
|"2-Headed Baby"||unknown||identical (conjoined)||male|
Notes and references
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "Twin" on Wikipedia
- ↑ 2.0 2.1 Harry Potter and the Philosopher's Stone, Chapter 6
- ↑ 3.0 3.1 In the Pottermore article on Ilvermorny School of Witchcraft and Wizardry, Martha is stated to have been a Squib, while Rionach was a witch, indicating that they had different genetic makeups and thus were not identical twins.
- ↑ MinaLima Store - Circus Arcanus - Museum of Human Oddities Poster (see this image)
- ↑ In the Circus Arcanus poster, the twins are depicted as wearing sailor hats and shirts, fashions typically reserved for baby boys.
- ↑ Harry Potter and the Half-Blood Prince (film) (see this image)
- ↑ In the prop issue of Metro featured in the film Harry Potter and the Order of the Phoenix, Jack and Tom were described as being delivered simultaneously in a "bundle," most likely indicating they shared a single amniotic sac. Twins that share an amniotic sac (technically known as monoamniotic twins) are always identical.
- ↑ Harry Potter and the Order of the Phoenix (film) (see this image)
- ↑ Harry Potter and the Goblet of Fire, Chapter 12
- ↑ Pottermore - Writing by J.K. Rowling: "Ilvermorny School of Witchcraft and Wizardry"
- ↑ The Making of Harry Potter (see this image)
- ↑ J.K. Rowling on Twitter: "Fred was born first. I always thought that was obvious!"