These are often said to be men from the American South or from Appalachia, and the photo is often used to make fun of US White Southerners or hillbillies’ tendency to have sex with, marry and make babies with family members.
Actually the photo is from The Cape Horn region of South Africa (the whiter and more Dutch part of South Africa even today), and was taken around 1993 by Roger Ballen. These are two Afrikaner brothers. However, it is quite possible that their appearance is a result of inbreeding. Afrikaners have always been pretty “hillbillyish” as far as White folks go.
There are websites out there who will give you the names of the brothers, but I didn’t have time to look it up although I saw that information at one time recently.