Is there such a thing?
On my partner's side his mother has 3 brothers who all have severe learning disabilities, to the extent that they live in sheltered accommodation, and have done all their adult lives. His mother seems to have emotional difficulties and/or mild learning disabilities, but there has been no official diagnosis. She has a sister who also seems unaffected.
My partner also has two brothers, of those brothers one demonstrates signs of mild learning disabilities. He is in his late 20's and has the mentality of a teenager. He didn't do well in school, and has never been able to hold down a job as an adult. Again he has not been officially diagnosed.
Can my OH go to the doctor and ask for genetic testing for any inherited conditions? I am quite sure that his mother would object to going herself.