"I would like to be 100," Kirk said when asked about his 98th birthday wish.
In a career spanning seven decades, Kirk has earned three Oscar nominations and an honorary Oscar in 1996.
In between making classic movies, Kirk had four sons (Michael, Eric, Joel and Peter), but his eldest and most famous son, Michael, seems to be the hardest to keep track of.
"I never know where he is," said Kirk, who nearly jumped out of his seat when Michael snuck up behind him during his interview.
"It's an inspirational career," Michael said of his dad. "He's probably one of the last of his great generation."
Their strong father-son bond was evident from the beginning, as seen in the home movies that Kirk shared with ET of Michael, now 70, as a little boy.
Kirk has an 11th book, Life Could Be Verse, going on sale Dec. 2 filled with his poetry, personal stories and family photos.
"Dad's history was that his father was not there," said Michael. "The one thing that he wanted to make sure that he did was to make that effort for his sons."
By Kirk's side through it all has been his wife, Anne. The couple have been married for 60 years and now are making a difference by building playgrounds in over 400 Los Angeles public schools.