A genetic counselor is consulted by a young man who is worried about developing huntington’s disease, an inherited disorder caused by a dominant allele of a single gene. The young man explains that his cousin was recently diagnosed with huntington’s disease, and the news has caused him to consider his own risk of developing the disorder. Which of the following questions will best help the genetic counselor to evaluate the risk of the young man developing huntington’s disease and transmitting it to his children?.