Inbreeding

"*Marvolo Gaunt, his son, Morfin, and his daughter, Merope Riddle (née Gaunt), were the last of the Gaunts, a very ancient wizarding family noted for a vein of instability and violence that flourished through the generations due to their habit of marrying their own cousins.*"
— Albus Dumbledore regarding inbreeding in the House of Gaunt
**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

"*The family has, however, eschewed the somewhat dangerous practice of inter-marrying within such a small pool of pure-bloods that they become enfeebled or unstable, unlike a small minority of fanatic families such as the Gaunts and Lestranges, and many a half-blood appears on the Malfoy family tree.*"
— Description of the Malfoy family

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, Brookstones, Lestranges, and Vanets but were still considered a "respectable" pure-blood family among said families.

## Side Effects

"*The man standing before them had thick hair so matted with dirt it could have been any colour. Several of his teeth were missing. His eyes were small and dark and stared in opposite directions.*"
— Morfin Gaunt demonstrates the physical ramifications of inbreeding

n 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.

### Brookstone Family

Stuart and Eura Brookstone were first cousins (their fathers Curtis and Artie were brothers) had been forced to marry by their parents in the early 19th century. Before them various members of the Brookstone family married their cousins to maintain blood purity.

### 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.

### House of Vanet

In desperation to keep with the tradition, the Vanets, have been known for marrying their third and fourth cousins.

## Known Incestuous Relationships

"*The pure-blood families are all interrelated. If you’re only going to let your sons and daughters marry purebloods your choice is very limited, there are hardly any of us left.*"
— Sirius Black to Harry Potter about the inbreeding practised by pure-blood families