Therefore all of the ancestors that Peter talks about who all inexplicably look exactly like him are Thelma's ancestors, not Francis's. This would explain the family resemblance. This troper's maternal grandparents both have the same last name of Martin (grandmother from North Carolina, grandfather from Ohio), so why couldn't Thelma and Francis have had the same last name as well? It's improbable, but definitely not impossible. * I personally assumed Thelma and Francis were related, like second cousins or something.