Mr. Kwon was portrayed by John Shin in the Season 1 episode
"...In Translation", and the Season 3 episode "D.O.C.".
Jin's mother was portrayed by Alexis Rhee in the
Season 3 episode "D.O.C.".
I have written to both Mr. Shin and Ms. Rhee, requesting autographs.
I'll update this post if/when I receive responses.