AFAIK we only have the DNA of one of his doubles. Otherwise one would have to get it from his grand/great-grand kids most of which are in the USA and have changed their last name. There were interviews with some of his grand kids but I don't know if it's on the internet. This was in the 90's.
This is me seriously asking - aren't these claims of autism, adhd etc. noting that correlation of genetic markers with the diagnosis, not causes of those diagnosis. Because the article seems to be saying that these markers can cause one or more of the diagnosis, which seems weird.