Inbreeding

Inbreeding is a practice in which someone marries and has children with someone who is in their own family. Inbreeding was a common practice for elite pure-blood wizarding families wishing to uphold the tradition of marrying only wizards of respected ancestry. It was noted that wizarding families became more diverse as time passed, as wizards began to marry half-bloods, Muggle-borns, and Muggles. Nevertheless, more conventional, elitist families tended to marry within their family, particularly cousins.
==Wizarding views==
Due to the dangers of inbreeding, many wizarding families eschewed such practices, particularly the Muggle-admiring Weasleys. By Hermione Granger's claim, there were not enough pure-bloods to compose the entire Death Eater organisation. Therefore, some of them were more likely half-bloods clinging onto their wizarding ancestries, pretending to be pure, furthering the rejection of inbreeding, even among the fanatics. Lord Voldemort was one of the most notorious examples.
The Malfoy family had been inclined to blood-purity since ancient times, though even they would not be willing to intermarry with cousins, believing the practice would endanger them, instead making them more willing to marry half-bloods. This differed them from the small minority families of the true fanatics such as the Gaunts, Blacks, and Lestranges, but were still considered a "respectable" pure-blood family among said families. 
==Side effects==
In Muggle genetics studies, it was proven that inbreeding could lead to serious problems. Notable effects that were seen in families are infertility (both in litter size and sperm viability), increased congenital defects (both mental and physical), fluctuating facial symmetry, decreased birth rate, increased offspring mortality, small adult size, loss of functioning immune systems and higher risks of cardiovascular diseases. It was evident in many wizarding families (e.g. the Gaunts, Blacks and Lestranges) that practise incest often display a high rate of mental instability.
Inbreeding also had a negative effect on a person's physical appearance. Marvolo Gaunt was short, and oddly proportioned, and his eyes, like those of his son and daughter, stared in opposite directions. Furthermore, Morfin Gaunt had an odd rolling gait. Merope Gaunt was likewise described as having a "plain, pale, rather heavy face". According to Mrs Cole, "she was no beauty".
Because of the implications of inbreeding, the families claiming to be pure were declining in the 20th century.
==Inbred families==
===House of Black===
The House of Black's family motto was "Toujours pur" (English: always pure). Therefore, the family was strictly traditionalised to marry other families (failing this, extremely rich families). The Black family took their motto seriously, and all family members who did not conform with the Black views of pure-blood supremacy or happened to be Squibs were disowned quickly and removed from the Black family tapestry.
In desperation to keep with the tradition, the Blacks, at one known point, resorted to extremes. Orion and Walburga Black were second cousins (their grandfathers Sirius and Cygnus were brothers) who married and had two children together.
Due to the Black family tree tapestry being so large, it was possible that many related people married without knowing about their relationship. For instance, Victoire Weasley and Teddy Lupin became romantically involved without anyone mentioning or realising that they were fourth cousins once removed through the Blacks.
===House of Gaunt===
The House of Gaunt had a fanatical belief in blood-purity, stemming from their esteemed ancestors Salazar Slytherin and Cadmus Peverell. To maintain their heritage's purity, they tended to marry their own cousins, which also allowed them to pass down Slytherin's Parseltongue ability.
This led many members of the family to deteriorate mentally and physiologically, and they squandered much of their family gold long before the 1920s. As such, Marvolo Gaunt and his son suffered much mental instability, accompanied with violence, and disproportionate bodily appearances. By the 20th century the family was living in poverty, in a small destitute shack.
===Lestrange family===
The bloodline of Corvus Lestrange I also practised inbreeding, as his youngest grandson Corvus married his cousin Eglantine Lestrange, and their son (another Corvus) married his cousin Clarisse Tremblay. Separately, Fulcran Lestrange III was also married to his second cousin once removed, Quintilla Lestrange.
==Known incestuous relationships==
 
Wizard(s) 	Notes
Orion Black 	Orion and his wife Walburga were second cousins through their mutual great-grandparents Phineas Nigellus Black and Ursula Flint. They were the parents of Sirius and Regulus Black.
Walburga Black 	Orion and his wife Walburga were second cousins through their mutual great-grandparents Phineas Nigellus Black and Ursula Flint. They were the parents of Sirius and Regulus Black.
House of Gaunt 	Various members of the House of Gaunt married their cousins to maintain blood purity.
Corvus Lestrange III	Corvus and his wife Eglantine were first cousins. Their fathers Corvus and Falco were brothers.
Eglantine Lestrange 	Corvus and his wife Eglantine were first cousins. Their fathers Corvus and Falco were brothers.
Corvus Lestrange IV 	Corvus and his wife Clarisse were first cousins. Their mothers Eglantine and Leonie were sisters. They were also related by Corvus' paternal grandfather and Clarisse's maternal grandfather, who were brothers.
Clarisse Tremblay 	Corvus and his wife Clarisse were first cousins. Their mothers Eglantine and Leonie were sisters. They were also related by Corvus' paternal grandfather and Clarisse's maternal grandfather, who were brothers.
Fulcran Lestrange 	Fulcran and his wife Quintilla were second cousins once removed. Quintilla's paternal great-great grandparents were also Fulcran's paternal great-grandparents.
Quintilla Lestrange 	Fulcran and his wife Quintilla were second cousins once removed. Quintilla's paternal great-great grandparents were also Fulcran's paternal great-grandparents.
==Behind the scenes==
*In the Epilogue of , Victoire Weasley and Edward Lupin are in a relationship. Both individuals are distantly fourth cousins once removed through the House of Black. However, this distant of a relationship is not usually considered incestuous.
==Appearances==
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==Notes and references==
Category:Procreation
Category:An Pure-Blood Supremacism