The correct answer is: Twelve of the characters in “A Family Reunion” were murder victims in a Rex Stout “Nero Wolfe” story. 

Clue #1

Over 100 clues there are to see.

But all are after Chapter three!

The names are mentioned several hundred times in the book but the first introduction of the theme was the appearance of “Thomas Yeager” who met his demise in “Too Many Clients.”

Clue #2

Not all were hit over the head

But all of them are quite dead.

The people all died in a variety of ways

Clue #3

To get this one you must be hard core

In the ways of pulp mystery fiction lore

It is unlikely anyone who is not a Rex Stout/Nero Wolfe fan would ever get this joke. 

Clue #4

A girl from the sewer found a buckeye on the street.

Kari and Timothy played them both quite sweet.

Lilly Rowan’s father made his fortune by building the NYC sewer system. Archie Goodwin is from Lima, Ohio. In the Fabulous A&E Nero Wolfe series, Kari Matchett played Lilly and Timothy Hutton played Archie.

Clue #5

Roses are red and so is the chair

Many of them even sat there.

In Nero’s office the “Red leather chair” is the one directly across from Nero and where Archie always put the most important person in the room.

Clue #6

After the boy caused the dent

Of course, orchids were sent

Peter Drossos was a young paperboy who had teamed up with Nero but was run down in the street by a car.  Drossos is the only member of the “Water Works” team we’ll never meet. Like his namesake, he died young. The big clue here is the orchids. If you don’t know why, then you’ve obviously never read a single Nero Wolfe novel.

Clue #7

A dozen are there plainly to see.

Brought back from the dead for you by me.

Thomas Yeager “Too Many Clients”

Kenneth Rennert “Plot it Yourself”

Barry Hazen “Homicide Trinity”

Clyde Osgood “Some Buried Caesar”

Cheney Boone “The Silent Speaker”

Cyril Orchard “And Be a Villain”

Pete Drossos “The Golden Spiders”

Noel Hawthorn “Where There’s a Will”

Bertha Aaron   “Homicide Trinity”

Kurt Bottweill “And Four to Go”

Louis Dahlmann “Before Midnight” I changed it to Simon to avoid a name ending with an “s”. I hate seeing “Louis’s”.

Michael Molloy “Might as Well be Dead” I changed it to Jimmy to avoid two Michaels

In addition, “Shane O’Reilly” and “Kevin Fox” were lead characters in my “Devon’s Way” series in the 1980s.