sewall wright's paternal grandfather (http://www.geni.com/people/John-Seward-Wright/6000000010506000055 …) and maternal grandmother (http://www.geni.com/people/Mary-Vashon-Wright-1838-79-Sewall/6000000010516510463 …) were brother and sister
@aClassicLiberal (in fact, when ind rev was underway, cousin marriage rates in europe went up! see 2nd half here: https://hbdchick.wordpress.com/2011/09/02/inbreeding-in-spain-in-the-19th-20th-centuries/ …)