Concept and analysis of Pedigree
I-3 can be either A'A' or AA'. In Huntington's disease or Achondroplasia, the father could still survive to adulthood and reproduce. If the father had a chromosomal disorder such as Kallman's syndrome, he would be unable to reproduce. However, this is not a simple mutation, and it is not heritable. You should ask your instructor to clearly define the problem.