First of all is the protagonist, octogenarian Paul Jacobson. He comes across as a curmudgeon but underneath has a heart of gold. In spite of short-term memory loss, he becomes an amateur sleuth and even has a romance with a young chick in her seventies.
Second is Paul’s granddaughter, Jennifer. She helps her grandfather solve crimes, and in later books in the series, they tell each other politically incorrect geezer jokes.
Next is Henry Palmer. Henry is on the autism spectrum, lacks social graces, and has a keen sense of observation. Paul and Henry have a running insult fest.
Finally, introduced in book five of the series, we have Madeline Hightower. She is a force of nature and marries Henry.
All of these characters contribute to the story and have their comedic elements.