It is the son.
I have some friends who are famous actors. They are all still alive, but have died on the screen several times over.
"Sorry, don't know where I got the grandson thing...
It is the son."
The grandson, who is the son of one of Flynn's daughters named Rory, is a teenage actor who's on a Nickelodeon series. His father is an Israeli named Gideon Amir.
http://www.seanflynn.org/seanflynn.html