@efevotu1988
Hi, I realize your question is almost a year old, and you may have already found an answer, but I wanted to share some information that might still be helpful.
Both Autism and ADHD are now well-established as largely hereditary conditions. While approximately 20% of cases result from spontaneous genetic mutations, research suggests that 70–90% are inherited. When inherited, the severity of symptoms is thought to depend on the specific location and number of gene variations passed down from the parents.
Given that both of your grandchildren are neurodiverse, it is reasonable to suspect a hereditary pattern within your family. This doesn't necessarily mean that one or both parents have a formal diagnosis; they may simply carry the relevant gene variations without displaying symptoms significant enough to warrant one, or they may exhibit only mild traits that fall below the diagnostic threshold.