How do you know they didn't? Until someone compiles a cluster of symptoms and identifies a probable cause, who is going to say that someone's symptoms are caused by lead or not? -- And besides, if they really did have it, their symptoms would probably have precluded them from marrying and becoming parents (and then grandparents); in the not-so-distant past, anyone with lead poisoning might have been imprisoned, or more likely, sent to a mental asylum: 'There are many different health effects associated with elevated blood lead levels. Young children under the age of six are especially vulnerable to lead's harmful health effects, because their brains and central nervous system are still being formed. For them, even very low levels of exposure can result in reduced IQ, learning disabilities, attention deficit disorders, behavioral problems, stunted growth, impaired hearing, and kidney damage. At high levels of exposure, a child may become mentally retarded, fall into a coma, and even die from lead poisoning. from http://www.nsc.org/library/facts/lead.htm In either case, their likelihood of reproducing or being a continuing part of your family history is very low. Far more people suffered from this condition than is generally known.